cephalic presentation a normal delivery

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The way a baby is positioned in the uterus just before birth can have a big effect on labor and delivery. This positioning is called fetal presentation.

Babies twist, stretch and tumble quite a bit during pregnancy. Before labor starts, however, they usually come to rest in a way that allows them to be delivered through the birth canal headfirst. This position is called cephalic presentation. But there are other ways a baby may settle just before labor begins.

Following are some of the possible ways a baby may be positioned at the end of pregnancy.

Head down, face down

When a baby is head down, face down, the medical term for it is the cephalic occiput anterior position. This the most common position for a baby to be born in. With the face down and turned slightly to the side, the smallest part of the baby's head leads the way through the birth canal. It is the easiest way for a baby to be born.

Head down, face up

When a baby is head down, face up, the medical term for it is the cephalic occiput posterior position. In this position, it might be harder for a baby's head to go under the pubic bone during delivery. That can make labor take longer.

Most babies who begin labor in this position eventually turn to be face down. If that doesn't happen, and the second stage of labor is taking a long time, a member of the health care team may reach through the vagina to help the baby turn. This is called manual rotation.

In some cases, a baby can be born in the head-down, face-up position. Use of forceps or a vacuum device to help with delivery is more common when a baby is in this position than in the head-down, face-down position. In some cases, a C-section delivery may be needed.

Frank breech

When a baby's feet or buttocks are in place to come out first during birth, it's called a breech presentation. This happens in about 3% to 4% of babies close to the time of birth. The baby shown below is in a frank breech presentation. That's when the knees aren't bent, and the feet are close to the baby's head. This is the most common type of breech presentation.

If you are more than 36 weeks into your pregnancy and your baby is in a frank breech presentation, your health care professional may try to move the baby into a head-down position. This is done using a procedure called external cephalic version. It involves one or two members of the health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

If the procedure isn't successful, or if the baby moves back into a breech position, talk with a member of your health care team about the choices you have for delivery. Most babies in a frank breech position are born by planned C-section.

Complete and incomplete breech

A complete breech presentation, as shown below, is when the baby has both knees bent and both legs pulled close to the body. In an incomplete breech, one or both of the legs are not pulled close to the body, and one or both of the feet or knees are below the baby's buttocks. If a baby is in either of these positions, you might feel kicking in the lower part of your belly.

If you are more than 36 weeks into your pregnancy and your baby is in a complete or incomplete breech presentation, your health care professional may try to move the baby into a head-down position. This is done using a procedure called external cephalic version. It involves one or two members of the health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

If the procedure isn't successful, or if the baby moves back into a breech position, talk with a member of your health care team about the choices you have for delivery. Many babies in a complete or incomplete breech position are born by planned C-section.

When a baby is sideways — lying horizontal across the uterus, rather than vertical — it's called a transverse lie. In this position, the baby's back might be:

• Down, with the back facing the birth canal.
• Sideways, with one shoulder pointing toward the birth canal.
• Up, with the hands and feet facing the birth canal.

Although many babies are sideways early in pregnancy, few stay this way when labor begins.

If your baby is in a transverse lie during week 37 of your pregnancy, your health care professional may try to move the baby into a head-down position. This is done using a procedure called external cephalic version. External cephalic version involves one or two members of your health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

If the procedure isn't successful, or if the baby moves back into a transverse lie, talk with a member of your health care team about the choices you have for delivery. Many babies who are in a transverse lie are born by C-section.

If you're pregnant with twins and only the twin that's lower in the uterus is head down, as shown below, your health care provider may first deliver that baby vaginally.

Then, in some cases, your health care team may suggest delivering the second twin in the breech position. Or they may try to move the second twin into a head-down position. This is done using a procedure called external cephalic version. External cephalic version involves one or two members of the health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

Your health care team may suggest delivery by C-section for the second twin if:

• An attempt to deliver the baby in the breech position is not successful.
• You do not want to try to have the baby delivered vaginally in the breech position.
• An attempt to move the baby into a head-down position is not successful.
• You do not want to try to move the baby to a head-down position.

In some cases, your health care team may advise that you have both twins delivered by C-section. That might happen if the lower twin is not head down, the second twin has low or high birth weight as compared to the first twin, or if preterm labor starts.

• Landon MB, et al., eds. Normal labor and delivery. In: Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Elsevier; 2021. https://www.clinicalkey.com. Accessed May 19, 2023.
• Holcroft Argani C, et al. Occiput posterior position. https://www.updtodate.com/contents/search. Accessed May 19, 2023.
• Frequently asked questions: If your baby is breech. American College of Obstetricians and Gynecologists https://www.acog.org/womens-health/faqs/if-your-baby-is-breech. Accessed May 22, 2023.
• Hofmeyr GJ. Overview of breech presentation. https://www.updtodate.com/contents/search. Accessed May 22, 2023.
• Strauss RA, et al. Transverse fetal lie. https://www.updtodate.com/contents/search. Accessed May 22, 2023.
• Chasen ST, et al. Twin pregnancy: Labor and delivery. https://www.updtodate.com/contents/search. Accessed May 22, 2023.
• Cohen R, et al. Is vaginal delivery of a breech second twin safe? A comparison between delivery of vertex and non-vertex second twins. The Journal of Maternal-Fetal & Neonatal Medicine. 2021; doi:10.1080/14767058.2021.2005569.
• Marnach ML (expert opinion). Mayo Clinic. May 31, 2023.

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What Is Cephalic Position?

The ideal fetal position for labor and delivery

• Why It's Best

Risks of Other Positions

• Determining Position
• Turning a Fetus

The cephalic position is when a fetus is head down when it is ready to enter the birth canal. This is one of a few variations of how a fetus can rest in the womb and is considered the ideal one for labor and delivery.

About 96% of babies are born in the cephalic position. Most settle into it between the 32nd and 36th weeks of pregnancy . Your healthcare provider will monitor the fetus's position during the last weeks of gestation to ensure this has happened by week 36.

If the fetus is not in the cephalic position at that point, the provider may try to turn it. If this doesn't work, some—but not all—practitioners will attempt to deliver vaginally, while others will recommend a Cesarean (C-section).

Getty Images

Why Is the Cephalic Position Best?

During labor, contractions dilate the cervix so the fetus has adequate room to come through the birth canal. The cephalic position is the easiest and safest way for the baby to pass through the birth canal.

If the fetus is in a noncephalic position, delivery becomes more challenging. Different fetal positions have a range of difficulties and varying risks.

A small percentage of babies present in noncephalic positions. This can pose risks both to the fetus and the mother, and make labor and delivery more challenging. It can also influence the way in which someone can deliver.

A fetus may actually find itself in any of these positions throughout pregnancy, as the move about the uterus. But as they grow, there will be less room to tumble around and they will settle into a final position.

It is at this point that noncephalic positions can pose significant risks.

Cephalic Posterior

A fetus may also present in an occiput or cephalic posterior position. This means they are positioned head down, but they are facing the abdomen instead of the back.

This position is also nicknamed "sunny-side up."

Presenting this way increases the chance of a painful and prolonged delivery.

There are three different types of breech fetal positioning:

• Frank breech: The legs are up with the feet near the head.
• Footling breech: One or both legs is lowered over the cervix.
• Complete breech: The fetus is bottom-first with knees bent.

A vaginal delivery is most times a safe way to deliver. But with breech positions, a vaginal delivery can be complicated.

When a baby is born in the breech position, the largest part—its head—is delivered last. This can result in them getting stuck in the birth canal (entrapped). This can cause injury or death.

The umbilical cord may also be damaged or slide down into the mouth of the womb, which can reduce or cut off the baby's oxygen supply.

Some providers are still comfortable performing a vaginal birth as long as the fetus is doing well. But breech is always a riskier delivery position compared with the cephalic position, and most cases require a C-section.

Likelihood of a Breech Baby

You are more likely to have a breech baby if you:

• Go into early labor before you're full term
• Have an abnormally shaped uterus, fibroids , or too much amniotic fluid
• Are pregnant with multiples
• Have placenta previa (when the placenta covers the cervix)

Transverse Lie

In transverse lie position, the fetus is presenting sideways across the uterus rather than vertically. They may be:

• Down, with the back facing the birth canal
• With one shoulder pointing toward the birth canal
• Up, with the hands and feet facing the birth canal

If a transverse lie is not corrected before labor, a C-section will be required. This is typically the case.

Determining Fetal Position

Your healthcare provider can determine if your baby is in cephalic presentation by performing a physical exam and ultrasound.

In the final weeks of pregnancy, your healthcare provider will feel your lower abdomen with their hands to assess the positioning of the baby. This includes where the head, back, and buttocks lie

If your healthcare provider senses that the fetus is in a breech position, they can use ultrasound to confirm their suspicion.

Turning a Fetus So They Are in Cephalic Position

External cephalic version (ECV) is a common, noninvasive procedure to turn a breech baby into cephalic position while it's still in the uterus.

This is only considered if a healthcare provider monitors presentation progress in the last trimester and notices that a fetus is maintaining a noncephalic position as your delivery date approaches.

External Cephalic Version (ECV)

ECV involves the healthcare provider applying pressure to your stomach to turn the fetus from the outside. They will attempt to rotate the head forward or backward and lift the buttocks in an upward position. Sometimes, they use ultrasound to help guide the process.

The best time to perform ECV is about 37 weeks of pregnancy. Afterward, the fetal heart rate will be monitored to make sure it’s within normal levels. You should be able to go home after having ECV done.

ECV has a 50% to 60% success rate. However, even if it does work, there is still a chance the fetus will return to the breech position before birth.

Natural Methods For Turning a Fetus

There are also natural methods that can help turn a fetus into cephalic position. There is no medical research that confirms their efficacy, however.

• Changing your position: Sometimes a fetus will move when you get into certain positions. Two specific movements that your provider may recommend include: Getting on your hands and knees and gently rocking back and forth. Another you could try is pushing your hips up in the air while laying on your back with your knees bent and feet flat on the floor (bridge pose).
• Playing stimulating sounds: Fetuses gravitate to sound. You may be successful at luring a fetus out of breech position by playing music or a recording of your voice near your lower abdomen.
• Chiropractic care: A chiropractor can try the Webster technique. This is a specific chiropractic analysis and adjustment which enables chiropractors to establish balance in the pregnant person's pelvis and reduce undue stress to the uterus and supporting ligaments.
• Acupuncture: This is a considerably safe way someone can try to turn a fetus. Some practitioners incorporate moxibustion—the burning of dried mugwort on certain areas of the body—because they believe it will enhance the chances of success.

A Word From Verywell

While most babies are born in cephalic position at delivery, this is not always the case. And while some fetuses can be turned, others may be more stubborn.

This may affect your labor and delivery wishes. Try to remember that having a healthy baby, and staying well yourself, are your ultimate priorities. That may mean diverting from your best laid plans.

Speaking to your healthcare provider about turning options and the safest route of delivery may help you adjust to this twist and feel better about how you will move ahead.

Glezerman M. Planned vaginal breech delivery: current status and the need to reconsider . Expert Rev Obstet Gynecol. 2012;7(2):159-166. doi:10.1586/eog.12.2

Cleveland Clinic. Fetal positions for birth .

MedlinePlus. Breech birth .

UT Southwestern Medical Center. Can you turn a breech baby around?

The American College of Obstetricians and Gynecologists. If your baby is breech .

Roecker CB. Breech repositioning unresponsive to Webster technique: coexistence of oligohydramnios .  Journal of Chiropractic Medicine . 2013;12(2):74-78. doi:10.1016/j.jcm.2013.06.003

By Cherie Berkley, MS Cherie Berkley is an award-winning journalist and multimedia storyteller covering health features for Verywell.

5.1 Normal delivery

5.1.1 general recommendations.

Personnel should wear personal protective equipment (gloves, goggles, clothing and eye protection) to prevent infection from blood and other body fluids. 

Ensure a calm reassuring environment and provide the woman as much privacy as possible during examinations and delivery. Encourage her to move about freely if desired and to have a person of her choice to accompany her.

Anticipate the need for resuscitation at every birth. The necessary equipment should be ready at hand and ready for use.

5.1.2 Diagnosing the start of labour

• Onset of uterine contractions: intermittent, rhythmic pains accompanied by a hardening of the uterus, progressively increasing in strength and frequency;
• in a primipara, the cervix will first efface then, dilate;
• in a multipara, effacement and dilation occur simultaneously.

Repeated contractions without cervical changes should not be considered as the start of labour. Repeated contractions that are ineffective (unaccompanied by cervical changes) and irregular, which spontaneously stop and then possibly start up again, represent false labour. In this case, do not rupture the membranes, do not administer oxytocin.

Likewise, cervical dilation with few or no contractions should not be considered the start of labour. Multiparous women in particular may have a dilated cervix (up to 5 cm) at term before the onset of labour. If in doubt, in both cases, re-examine 4 hours later. If the cervix has not changed labour has not begun and the woman does not need to be admitted to the delivery room.

5.1.3 Stages of labour

First stage: dilation and foetal descent, divided into 2 phases.

1) Latent phase: from the start of labour to approximately 5 cm of dilation. Its duration varies depending on the number of prior deliveries. 2) Active phase: from approximately 5 cm to complete dilation [1] Citation 1. World Health Organization. WHO recommendations Intrapartum care for a positive childbirth experience, Geneva, 2018. http://apps.who.int/iris/bitstream/handle/10665/272447/WHO-RHR-18.12-eng.pdf?ua=1  [Accessed 18 june 2018] . During this phase the cervix dilates faster than during the latent phase. The time to dilate varies with the number of previous deliveries. As a rule, it does not last longer than 10 hours in a multipara and 12 hours in a primipara.

Second stage: delivery of the infant

Begins at full dilation.

Third stage: delivery of the placenta

See Chapter 8 .

5.1.4 First stage: dilation and descent of the foetus

The indicators being monitored are noted on the partograph ( Section 5.2 ).

Uterine contractions

• Contractions progressively increase in strength and frequency: sometimes 30 minutes apart early in labour; closer together (every 2 to 3 minutes) at the end of labour.
• A contraction can last up to a minute.
• The uterus should relax between contractions.
• Watch the shape of the uterus in order to spot a Bandl’s ring (Chapter 3, Section 3.3.2 ).

General condition of the patient

• Monitor the heart rate, blood pressure and temperature every 4 hours or more often in case of abnormality.
• Ask the woman to empty her bladder regularly (e.g. every 2 hours).
• Keep the woman hydrated (offer her water or tea).
• Encourage the woman to move about freely during labour. Position changes and walking around help relieve the pain, enhances the progress of labour and helps foetal descent. Pain can also be relieved by massage or hot or cold compresses. Midwife support helps manage pain.
• Routinely insert an IV line in the following situations: excessively large uterus (foetal macrosomia, multiple pregnancy or polyhydramnios), known anaemia and hypertension.

Foetal heart rate

Foetal heart rate monitoring.

Use a Pinard stethoscope or foetal Doppler, every 30 minutes during the active phase and every 5 minutes during active second stage, or as often as possible. Listen to and count for at least one whole minute immediately after the contraction. Normal foetal heart rate is 110 to 160 beats per minute. The foetal heart rate may slow down during a contraction. If it becomes completely normal again as soon as the uterus relaxes, there is probably no foetal distress. If the foetal heart rate heard immediately after the end of a contraction is abnormal (less than 100 beats per minute or more than 180 beats per minute), continue foetal heart rate monitoring for the next 3 contractions to confirm the abnormality.

Management of abnormal foetal heart rate

• Insert an IV line.
• Check maternal vital signs: heart rate, blood pressure and temperature.
• Check the uterine tonus. If hypertonic, look for excessive administration of oxytocin (which should therefore be stopped) or placental abruption (Chapter 3,  Section 3.2 ).
• Check the colour of the amniotic fluid: meconium-stained (greenish) amniotic fluid combined with foetal heart rate abnormalities is suggestive of true foetal distress.
• Stop administering oxytocin if an infusion is in progress.
• Check for vaginal bleeding: bleeding may suggest placental abruption or uterine rupture.
• Raise the patient or place her on her left side. Laying on her back the uterus creates pressure on the vena cava, which may be the cause of low foetal heart rate.
• Correct possible hypotension by fluid replacement (Ringer lactate) to bring the systolic blood pressure ≥ 90 mmHg.
• Perform a vaginal examination to look for cord prolapse.
• If the foetal heart rate is more than 180 beats/minute:

The most common cause is maternal febrile infection.

• Look for the cause of the infection (uterine infection, pyelonephritis, malaria, etc.) and treat. 
• Treat the fever (paracetamol).
• In case of fever of unknown origin, administer antibiotics as for a prolonged rupture of membranes (Chapter 4, Section 4.9 ).

If the abnormal foetal heart rate persists or the amniotic fluid becomes stained with meconium, deliver quickly. If the cervix is fully dilated and the head engaged, perform instrumental delivery (vacuum extractor or forceps, depending on the operator’s skill and experience); otherwise consider caesarean section.

Dilation during active phase

• The cervix should remain soft, and dilate progressively. Dilation should be checked by vaginal examination every 4 hours if there are no particular problems (Figures 5.2).
• No progress in cervical dilation between two vaginal examinations is a warning sign.
• Action must be taken if there is no progress for 4 hours: artificial rupture of membranes, administration of oxytocin,  caesarean section, depending on the circumstances.

Figures 5.2 - Estimating cervical dilation

Amniotic sac

• The amniotic sac bulges during contractions and usually breaks spontaneously after 5 cm of dilation or at full dilation during delivery. Immediately after rupture, check the foetal heart rate and if necessary perform a vaginal examination in order to identify a potential prolapse of the umbilical cord ( Section 5.4 ). Once the membranes are ruptured, always use sterile gloves for vaginal examination.
• Note the colour of the amniotic fluid: clear, blood-stained, or meconium-stained.
• Meconium staining by itself, without abnormal foetal heart rate, is not diagnostic of foetal distress, but does require closer monitoring—in particular, a vaginal examination every 2 hours. Action must be taken if dilation fails to progress after 2 hours.

Foetal progress

• Assess foetal descent by palpating the abdomen (portion of the foetal head felt above the symphysis pubis) before performing the vaginal examination.
• At each vaginal examination, in addition to dilation, check the presentation, the position and the degree of foetal descent.
• Look for signs that the foetal head is engaged:

On vaginal examination, the presenting part prevents the examiner's fingers from reaching the sacral concavity (Figures 5.3a and 5.3b). The presence of caput (benign diffuse swelling of the foetal head) can lead to the mistaken conclusion that the foetal head is engaged. The distance between the foetal shoulder and the upper edge of the symphysis pubis is less than 2 finger widths (Figures 5.3c and 5.3d).

• Use reference points on the foetal skull to determine the position of the head in the mother's pelvis. It is easier to determine the position of the head after the membranes have ruptured, and the cervix is more than 5 cm dilated. When the head is well flexed, the anterior (diamond-shaped) fontanelle is not palpable; only the sagittal suture and the posterior (triangular) fontanelle are. The posterior fontanelle is the landmark for the foetal occiput, and thus helps give the foetal position. In most cases, once the head is engaged, rotation of the head within the pelvis brings the foetal occiput under the mother's symphysis, with the posterior fontanelle along the anterior midline.

5.1.5 Second stage: delivery of the infant

This stage is often rapid in a multipara, and slower in a primipara. It should not, however, take longer than 2 hours in a multipara and 3 hours in a primipara

If there is a traditional delivery position and no specific risk for the mother or child has been established, it is possible to assist a delivery in a woman on her back, on her left side, squatting or on all fours (Figures 5.4).

Figures 5.4 - Delivery position

• Rinse the vulva and perineum with clean water.
• The bladder should be emptied, naturally if possible. In cases of urinary retention only, insert a urinary catheter using sterile technique (sterile gloves; sterile, single use catheter).
• If labour is progressing well and there is no foetal heart rate abnormality, let the woman follow her own urge to push. In other cases, expulsive effort should be directed. The woman should push during the uterine contraction. Pushing may be done either with held breath (after a deep inhalation, glottis closed, abdominal muscles and diaphragm contracted, directed toward the perineum) or with exhalation. Expulsive effort is maintained for long as possible: in general, 2 to 3 pushes per contraction.
• Between contractions, the woman should rest and breathe deeply. The birth attendant should monitor the foetal heart rate after each contraction.
• The head begins to stretch the perineum, which becomes progressively thinner; the vaginal opening distends, the labia spread apart, and the occiput appears. In a cephalic presentation, the head usually emerges occiput anterior: the infant is born looking down, the occiput pivoting against the symphysis (Figures 5.5). The head goes into slight extension. The birth attendant must guide this motion and prevent any abrupt expulsive movement, with one hand supporting the occiput. The other hand can support the chin through the perineum. Cover the anal area with a compress (Figures 5.6).

During this final phase—an active one for the birth attendant—the woman should stop all expulsive efforts and breathe deeply. With one hand, the birth attendant controls the extension of the head and moves it slightly side-to-side, in order to gradually free the parietal protuberances; if necessary (not routinely), the chin can be lifted with the other hand (Figure 5.7).

• At the moment of delivery, the perineum is extremely distended. Controlling the expulsion can help reduce the risk of a tear. Episiotomy ( Section 5.8 ) is not routinely indicated. In an occiput-posterior delivery (Figure 5.8), where perineal distension is at a maximum, episiotomy may be helpful.

• The head, once delivered, rotates spontaneously by at least 90°. The birth attendant helps this movement by grasping the head in both hands and exerting gentle downward traction to bring the anterior shoulder under the symphysis and then deliver it then, smooth upward traction to deliver the posterior shoulder (Figures 5.9).

To reduce the risk of perineal tears, control the delivery of the posterior shoulder.

• Place the neonate on mother's chest. For neonatal care, see Chapter 10,  Section 10.1 .

5.1.6 Oxytocin administration

Administer oxytocin to the mother immediately and then deliver the placenta (Chapter 8, Section 8.1.2 ).

5.1.7 Umbilical cord clamping

See Chapter 10,  Section 10.1.1 .

• 1. World Health Organization. WHO recommendations Intrapartum care for a positive childbirth experience, Geneva, 2018. http://apps.who.int/iris/bitstream/handle/10665/272447/WHO-RHR-18.12-eng.pdf?ua=1  [Accessed 18 june 2018]

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INTRODUCTION

Diagnosis and management of face and brow presentations will be reviewed here. Other cephalic malpresentations are discussed separately. (See "Occiput posterior position" and "Occiput transverse position" .)

Prevalence  —  Face and brow presentation are uncommon. Their prevalences compared with other types of malpresentations are shown below [ 1-9 ]:

● Occiput posterior – 1/19 deliveries

● Breech – 1/33 deliveries

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CHAPTER 22:  Normal Labor

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Fetal orientation.

• MECHANISMS OF LABOR
• NORMAL LABOR CHARACTERISTICS
• MANAGEMENT OF NORMAL LABOR
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Labor is the process that leads to childbirth. It begins with the onset of regular uterine contractions and ends with delivery of the newborn and expulsion of the placenta. Pregnancy and birth are physiological processes. Thus, labor and delivery should be considered normal for most women.

Fetal position within the birth canal is critical to labor progress and to the delivery route. It should be determined in early labor, and sonography can be implemented for unclear cases. Important relationships include fetal lie, presentation, attitude, and position.

Of these, fetal lie describes the relationship of the fetal long axis to that of the mother. In more than 99 percent of labors at term, the fetal lie is longitudinal . A transverse lie is less frequent. Occasionally, the fetal and maternal axes may cross at a 45-degree angle to form an oblique lie . This is unstable and becomes longitudinal or transverse during labor.

Fetal Presentation

The presenting part is the portion of the fetal body either within or in closest proximity to the birth canal. It usually can be felt through the cervix on vaginal examination. In longitudinal lies, the presenting part is either the fetal head or the breech, creating cephalic and breech presentations, respectively. When the fetus lies with the long axis transversely, the shoulder is considered the presenting part.

Cephalic presentations are subclassified according to the relationship between the head and body of the fetus ( Fig. 22-1 ). Ordinarily, the head is flexed sharply so that the chin contacts the thorax. The occipital fontanel is the presenting part, and this presentation is referred to as a vertex or occiput presentation . Much less often, the fetal neck may be sharply extended so that the occiput and back come into contact, and the face is foremost in the birth canal— face presentation . The fetal head may assume a position between these extremes. When the neck is only partly flexed, the anterior (large) fontanel may present— sinciput presentation . When the neck is only partially extended, the brow may emerge— brow presentation . These latter two are usually transient. As labor progresses, sinciput and brow presentations almost always convert into occiput or face presentations by neck flexion or extension, respectively. If not, dystocia can develop ( Chap. 23 , p. 441).

FIGURE 22-1

Longitudinal lie, cephalic presentation. Differences in attitude of the fetal body in (A) occiput, (B) sinciput, (C) brow, and (D) face presentations. Note changes in fetal attitude as the fetal head becomes less flexed.

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Fetal Presentation, Position, and Lie (Including Breech Presentation)

, MD, Children's Hospital of Philadelphia

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Abnormal fetal lie or presentation may occur due to fetal size, fetal anomalies, uterine structural abnormalities, multiple gestation, or other factors. Diagnosis is by examination or ultrasonography. Management is with physical maneuvers to reposition the fetus, operative vaginal delivery Operative Vaginal Delivery Operative vaginal delivery involves application of forceps or a vacuum extractor to the fetal head to assist during the second stage of labor and facilitate delivery. Indications for forceps... read more , or cesarean delivery Cesarean Delivery Cesarean delivery is surgical delivery by incision into the uterus. The rate of cesarean delivery was 32% in the United States in 2021 (see March of Dimes: Delivery Method). The rate has fluctuated... read more .

Terms that describe the fetus in relation to the uterus, cervix, and maternal pelvis are

Fetal presentation: Fetal part that overlies the maternal pelvic inlet; vertex (cephalic), face, brow, breech, shoulder, funic (umbilical cord), or compound (more than one part, eg, shoulder and hand)

Fetal position: Relation of the presenting part to an anatomic axis; for transverse presentation, occiput anterior, occiput posterior, occiput transverse

Fetal lie: Relation of the fetus to the long axis of the uterus; longitudinal, oblique, or transverse

Normal fetal lie is longitudinal, normal presentation is vertex, and occiput anterior is the most common position.

Abnormal fetal lie, presentation, or position may occur with

Fetopelvic disproportion (fetus too large for the pelvic inlet)

Fetal congenital anomalies

Uterine structural abnormalities (eg, fibroids, synechiae)

Multiple gestation

Several common types of abnormal lie or presentation are discussed here.

Transverse lie

Fetal position is transverse, with the fetal long axis oblique or perpendicular rather than parallel to the maternal long axis. Transverse lie is often accompanied by shoulder presentation, which requires cesarean delivery.

Breech presentation

There are several types of breech presentation.

Frank breech: The fetal hips are flexed, and the knees extended (pike position).

Complete breech: The fetus seems to be sitting with hips and knees flexed.

Single or double footling presentation: One or both legs are completely extended and present before the buttocks.

Types of breech presentations

Breech presentation makes delivery difficult ,primarily because the presenting part is a poor dilating wedge. Having a poor dilating wedge can lead to incomplete cervical dilation, because the presenting part is narrower than the head that follows. The head, which is the part with the largest diameter, can then be trapped during delivery.

Additionally, the trapped fetal head can compress the umbilical cord if the fetal umbilicus is visible at the introitus, particularly in primiparas whose pelvic tissues have not been dilated by previous deliveries. Umbilical cord compression may cause fetal hypoxemia.

Predisposing factors for breech presentation include

Preterm labor Preterm Labor Labor (regular uterine contractions resulting in cervical change) that begins before 37 weeks gestation is considered preterm. Risk factors include prelabor rupture of membranes, uterine abnormalities... read more

Multiple gestation Multifetal Pregnancy Multifetal pregnancy is presence of > 1 fetus in the uterus. Multifetal (multiple) pregnancy occurs in up to 1 of 30 deliveries. Risk factors for multiple pregnancy include Ovarian stimulation... read more

Uterine abnormalities

Fetal anomalies

If delivery is vaginal, breech presentation may increase risk of

Umbilical cord prolapse

Perinatal death

It is best to detect abnormal fetal lie or presentation before delivery. During routine prenatal care, clinicians assess fetal lie and presentation with physical examination in the late third trimester. Ultrasonography can also be done. If breech presentation is detected, external cephalic version can sometimes move the fetus to vertex presentation before labor, usually at 37 or 38 weeks. This technique involves gently pressing on the maternal abdomen to reposition the fetus. A dose of a short-acting tocolytic ( terbutaline 0.25 mg subcutaneously) may help. The success rate is about 50 to 75%. For persistent abnormal lie or presentation, cesarean delivery is usually done at 39 weeks or when the woman presents in labor.

Face or brow presentation

In face presentation, the head is hyperextended, and position is designated by the position of the chin (mentum). When the chin is posterior, the head is less likely to rotate and less likely to deliver vaginally, necessitating cesarean delivery.

Brow presentation usually converts spontaneously to vertex or face presentation.

Occiput posterior position

The most common abnormal position is occiput posterior.

The fetal neck is usually somewhat deflexed; thus, a larger diameter of the head must pass through the pelvis.

Progress may arrest in the second phase of labor. Operative vaginal delivery Operative Vaginal Delivery Operative vaginal delivery involves application of forceps or a vacuum extractor to the fetal head to assist during the second stage of labor and facilitate delivery. Indications for forceps... read more or cesarean delivery Cesarean Delivery Cesarean delivery is surgical delivery by incision into the uterus. The rate of cesarean delivery was 32% in the United States in 2021 (see March of Dimes: Delivery Method). The rate has fluctuated... read more is often required.

Position and Presentation of the Fetus

If a fetus is in the occiput posterior position, operative vaginal delivery or cesarean delivery is often required.

In breech presentation, the presenting part is a poor dilating wedge, which can cause the head to be trapped during delivery, often compressing the umbilical cord.

For breech presentation, usually do cesarean delivery at 39 weeks or during labor, but external cephalic version is sometimes successful before labor, usually at 37 or 38 weeks.

Drugs Mentioned In This Article

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Pelvimetry for fetal cephalic presentations at or near term for deciding on mode of delivery

Pelvimetry assesses the size of a woman's pelvis aiming to predict whether she will be able to give birth vaginally or not. This can be done by clinical examination, or by conventional X‐rays, computerised tomography (CT) scanning, or magnetic resonance imaging (MRI).

To assess the effects of pelvimetry (performed antenatally or intrapartum) on the method of birth, on perinatal mortality and morbidity, and on maternal morbidity. This review concentrates exclusively on women whose fetuses have a cephalic presentation.

Search methods

We searched Cochrane Pregnancy and Childbirth Group's Trials Register (31 January 2017) and reference lists of retrieved studies.

Selection criteria

Randomised controlled trials (including quasi‐randomised) assessing the use of pelvimetry versus no pelvimetry or assessing different types of pelvimetry in women with a cephalic presentation at or near term were included. Cluster trials were eligible for inclusion, but none were identified.

Data collection and analysis

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We assessed the quality of the evidence using the GRADE approach.

Main results

Five trials with a total of 1159 women were included. All used X‐ray pelvimetry to assess the pelvis. X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that examined other types of radiological pelvimetry or that compared clinical pelvimetry versus no pelvimetry.

The included trials were generally at high risk of bias. There is an overall high risk of performance bias due to lack of blinding of women and staff. Two studies were also at high risk of selection bias. We used GRADEpro software to grade evidence for our selected outcomes; for caesarean section we rated the evidence low quality and all the other outcomes (perinatal mortality, wound sepsis, blood transfusion, scar dehiscence and admission to special care baby unit) as very low quality. Downgrading was due to risk of bias relating to lack of allocation concealment and blinding, and imprecision of effect estimates.

Women undergoing X‐ray pelvimetry were more likely to have a caesarean section (risk ratio (RR) 1.34, 95% confidence interval (CI) 1.19 to 1.52; 1159 women; 5 studies; low‐quality evidence ). There were no clear differences between groups for perinatal outcomes: perinatal mortality (RR 0.53, 95% CI 0.19 to 1.45; 1159 infants; 5 studies; very low‐quality evidence ), perinatal asphyxia (RR 0.66, 95% CI 0.39 to 1.10; 305 infants; 1 study), and admission to special care baby unit (RR 0.20, 95% CI 0.01 to 4.13; 288 infants; 1 study; very low‐quality evidence ). Other outcomes assessed were wound sepsis (RR 0.83, 95% CI 0.26 to 2.67; 288 women; 1 study; very low‐quality evidence ), blood transfusion (RR 1.00, 95% CI 0.39 to 2.59; 288 women; 1 study; very low‐quality evidence ), and scar dehiscence (RR 0.59, 95% CI 0.14 to 2.46; 390 women; 2 studies; very low‐quality evidence ). Again, no clear differences were found for these outcomes between the women who received X‐ray pelvimetry and those who did not. Apgar score less than seven at five minutes was not reported in any study.

Authors' conclusions

X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that used other types or pelvimetry (other radiological examination or clinical pelvimetry versus no pelvimetry). There is not enough evidence to support the use of X‐ray pelvimetry for deciding on mode of delivery in women whose fetuses have a cephalic presentation. Women who undergo an X‐ray pelvimetry may be more likely to have a caesarean section.

Further research should be directed towards defining whether there are specific clinical situations in which pelvimetry can be shown to be of value. Newer methods of pelvimetry (CT, MRI) should be subjected to randomised trials to assess their value. Further trials of X‐ray pelvimetry in cephalic presentations would be of value if large enough to assess the effect on perinatal mortality.

Plain language summary

What is the issue?

Does the use of pelvimetry to assess the size of the woman's pelvis improve outcomes for baby and mother? Pelvimetry might identify babies whose heads are too big for their mother's pelvis. In this case, an elective caesarean section might improve the outcome. Forms of pelvimetry include radiological pelvimetry (X‐ray, computerised tomography (CT) scan or magnetic resonance imaging (MRI)) and clinical examination of the woman. We planned to include all studies comparing the use of clinical or radiological (X‐ray, CT or MRI) pelvimetry versus no pelvimetry, or different types of pelvimetry.

Why is this important?

Sometimes, normal labour does not progress because the baby's head is too big, or the pelvis of the mother is too small, for the baby to pass through. This is called "cephalo‐pelvic disproportion" or "obstructed labour" which may lead to an emergency caesarean section with possible risks for both mother and baby. A pregnant mother or her caregiver might be worried that disproportion could occur and for this reason, pelvimetry can be performed either before or during labour. It can be undertaken by clinical examination, X‐ray, CT‐scan or MRI. Pelvimetry measures the diameters of the pelvis and the baby's head. However, doing a pelvimetry also has implications: clinical examination might be very uncomfortable for the mother, X‐ray and CT‐scanning might be harmful for the baby and MRI is very expensive. All of these techniques have to be performed meticulously by experienced and skilled people to have any real value.

If we could diagnose the disproportion accurately before birth using pelvimetry, we might reduce the need for an emergency caesarean section and plan an elective procedure, with better outcomes for the baby and less complications for the mother.

What evidence did we find?

We searched for evidence on 30th November 2016 and identified five trials with a total of 1159 pregnant women. All five trials used X‐ray pelvimetry in comparison to no X‐ray pelvimetry.

The women who received X‐ray pelvimetry were more likely to have a caesarean section ( low‐quality evidence ). Whether a woman had pelvimetry or not, we found no difference in the numbers of babies that died ( very low‐quality evidence ), who did not have enough oxygen during labour, or were admitted to special care baby units ( very low‐quality evidence ). For the women, no differences were found between numbers of women with wound sepsis, those who received a blood transfusion, or those whose caesarean section scar began to break down ( all very low‐quality evidence ). Apgar score less than seven at five minutes was not reported in any study.

What does this mean?

There is too little evidence (the majority of which is low quality) to show whether measuring the size of the woman's pelvis (pelvimetry) is beneficial and safe when the baby is in a head‐down position. The number of women having a caesarean section increased if women had X‐ray pelvimetry but there was insufficient good‐quality evidence to show if pelvimetry improves outcomes for the baby. More research is needed.

Summary of findings

Description of the condition.

Cephalo‐pelvic disproportion (CPD) is one of the leading indications for an emergency caesarean section. CPD occurs when there is a mismatch between the fetal head and the maternal pelvis (when the fetal head is too big for the pelvis), resulting in obstructed labour.

Emergency caesarean sections have been shown to have an increased risk of maternal and neonatal morbidity and mortality ( van Ham 1997 ). Women undergoing an emergency caesarean section are at an increased risk for intra‐ and postoperative complications such as haemorrhage (tearing of the uterine incision into the parametrium or cervix, hysterotomy extension), infection (wound sepsis, endometritis), deep vein thrombosis and prolonged hospitalisation. Risks for the neonate include respiratory problems and trauma.

Women with a previous caesarean scar are known to be at risk for uterine rupture, stillbirth and placenta praevia in subsequent pregnancies. Performing a repeat caesarean section also increases the risk of bowel or bladder injury and haemorrhage and women who have had a previous caesarean section can be offered a trial of labour (vaginal birth after caesarean section (VBAC)) to reduce the intra‐ and postoperative complications of a caesarean section. However, the low but life‐threatening risk (for both mother and fetus) of a uterine rupture during labour has to be taken into consideration and explained to the woman ( Dodd 2013 ).

Description of the intervention

Assessment of the size of a woman's pelvis (pelvimetry) can be achieved by clinical examination (where the bony pelvis is digitally examined to identify prominent structures that may cause obstructed labour), or by conventional X‐rays (usually a lateral and anterior‐posterior view used to physically measure the sizes of the pelvic inlet, midpelvis and pelvic outlet, Morgan 1992 ), computerised tomography (CT) scanning (measuring the pelvis in the lateral, anterior‐posterior and axial views, Morris 1993 ), or magnetic resonance imaging (MRI, measuring of a midline sagittal, and oblique coronal views of the pelvis, Sporri 2002 ).

How the intervention might work

The aim of pelvimetry (whichever method is used) in women whose fetuses have a cephalic presentation, is to detect the presence of cephalo‐pelvic disproportion and therefore the need for caesarean section. Pelvimetry may influence clinical care since clinicians who feel that vaginal birth would be impossible, would offer the woman an elective caesarean section, thereby reducing the need of an emergency caesarean section. The criteria for determining an adequate or small pelvis have been from descriptive studies and senior opinions ( Mengert 1948 ).

Why it is important to do this review

These techniques are not without risks, the greatest of all being a false positive result and unnecessary caesarean section. Clinical pelvimetry is very uncomfortable for the woman, X‐rays and CT scanning expose the fetus to radiation (the latter slightly less so), and MRI is very expensive. All of these techniques have to be performed meticulously by experienced and skilled people in order to have any value at all.

To assess the effects of pelvimetry (performed antenatally, or intrapartum) on the method of birth, on perinatal mortality and morbidity, and on maternal morbidity. This review concentrates exclusively on women whose fetuses have a cephalic presentation.

Criteria for considering studies for this review

Types of studies

We included all randomised controlled trials (including quasi‐randomised) comparing pelvimetry in cephalic presentations versus no pelvimetry or comparing different types of pelvimetry. We would have included cluster trials if they had been identified during the search. Cross‐over studies were not eligible for this review.

If an abstract was of interest, we would have contacted the authors for further information about their trial.

Types of participants

Pregnant women with a singleton, cephalic presentation fetus who have or have not had a previous caesarean section. Studies that recruited women before, or during labour were included as well as women for spontaneous labour, induction of labour, or trial of scar after previous caesarean section (otherwise known as vaginal birth after caesarean or VBAC).

Types of interventions

The main intervention of interest is pelvimetry as a predictor of cephalo‐pelvic disproportion. Control groups could include women who did not have pelvimetry or who had different types of pelvimetry.

We planned to include studies comparing different methods of clinical or radiological pelvimetry such as X‐rays, computerised tomography (CT) scanning or magnetic resonance imaging (MRI). We reported women who have had one previous caesarean section and women who have had no previous section, or are nulliparous, in separate clinical subgroups.

Types of outcome measures

Primary outcomes, caesarean section, perinatal mortality, secondary outcomes, maternal outcomes, puerperal pyrexia, wound sepsis, blood transfusion, scar dehiscence, perinatal outcomes, perinatal asphyxia.

• Admission to special care baby units

Apgar score less than seven at five minutes

Search methods for identification of studies.

The following methods section of this review is based on a standard template used by Cochrane Pregnancy and Childbirth.

Electronic searches

We searched Cochrane Pregnancy and Childbirth’s Trials Register by contacting their Information Specialist (31 January 2017).

The Register is a database containing over 22,000 reports of controlled trials in the field of pregnancy and childbirth. For full search methods used to populate Pregnancy and Childbirth’s Trials Register including the detailed search strategies for CENTRAL, MEDLINE, Embase and CINAHL; the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service, please follow this link to the editorial information about the Cochrane Pregnancy and Childbirth in the Cochrane Library and select the ‘ Specialized Register ’ section from the options on the left side of the screen.

Briefly, Cochrane Pregnancy and Childbirth’s Trials Register is maintained by their Information Specialist and contains trials identified from:

• monthly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);
• weekly searches of MEDLINE (Ovid);
• weekly searches of Embase (Ovid);
• monthly searches of CINAHL (EBSCO);
• handsearches of 30 journals and the proceedings of major conferences;
• weekly current awareness alerts for a further 44 journals plus monthly BioMed Central email alerts.

Search results are screened by two people and the full text of all relevant trial reports identified through the searching activities described above is reviewed. Based on the intervention described, each trial report is assigned a number that corresponds to a specific Pregnancy and Childbirth review topic (or topics), and is then added to the Register. The Information Specialist searches the Register for each review using this topic number rather than keywords. This results in a more specific search set which has been fully accounted for in the relevant review sections ( Included studies ; Excluded studies ).

Searching other resources

We searched the reference lists of retrieved studies.

We did not apply any language or date restrictions.

For methods used in the previous version of this review, see Pattinson 1997 .

For this update, the following methods were used for assessing the two reports that were identified as a result of the updated search.

The following methods section of this review is based on a standard template used by Cochrane Pregnancy and Childbirth Group.

Selection of studies

Two review authors independently assessed for inclusion all the potential studies identified as a result of the search strategy. We resolved any disagreement through discussion or, if required, we consulted the third review author.

Data extraction and management

We designed a form to extract data. For eligible studies, two review authors extracted the data using the agreed form. We resolved discrepancies through discussion or, if required, we consulted the third review author. Data were entered into Review Manager software ( RevMan 2014 ) and checked for accuracy.

When information regarding any of the above was unclear, we planned to contact authors of the original reports to provide further details.

Assessment of risk of bias in included studies

Two review authors independently assessed risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions ( Higgins 2011 ). Any disagreement was resolved by discussion or by involving a third assessor.

(1) Random sequence generation (checking for possible selection bias)

We described for each included study the method used to generate the allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups.

We assessed the method as:

• low risk of bias (any truly random process, e.g. random number table; computer random number generator);
• high risk of bias (any non‐random process, e.g. odd or even date of birth; hospital or clinic record number);
• unclear risk of bias.

(2) Allocation concealment (checking for possible selection bias)

We described for each included study the method used to conceal allocation to interventions prior to assignment and assessed whether intervention allocation could have been foreseen in advance of, or during recruitment, or changed after assignment.

We assessed the methods as:

• low risk of bias (e.g. telephone or central randomisation; consecutively numbered sealed opaque envelopes);
• high risk of bias (open random allocation; unsealed or non‐opaque envelopes, alternation; date of birth);

(3.1) Blinding of participants and personnel (checking for possible performance bias)

We described for each included study the methods used, if any, to blind study participants and personnel from knowledge of which intervention a participant received. We considered that studies were at low risk of bias if they were blinded, or if we judged that the lack of blinding unlikely to affect results. We assessed blinding separately for different outcomes or classes of outcomes.

• low, high or unclear risk of bias for participants;
• low, high or unclear risk of bias for personnel.

(3.2) Blinding of outcome assessment (checking for possible detection bias)

We described for each included study the methods used, if any, to blind outcome assessors from knowledge of which intervention a participant received. We assessed blinding separately for different outcomes or classes of outcomes.

We assessed methods used to blind outcome assessment as:

• low, high or unclear risk of bias.

(4) Incomplete outcome data (checking for possible attrition bias due to the amount, nature and handling of incomplete outcome data)

We described for each included study, and for each outcome or class of outcomes, the completeness of data including attrition and exclusions from the analysis. We stated whether attrition and exclusions were reported and the numbers included in the analysis at each stage (compared with the total randomised participants), reasons for attrition or exclusion where reported, and whether missing data were balanced across groups or were related to outcomes. Where sufficient information was reported, or could be supplied by the trial authors, we planned to re‐include missing data in the analyses which we undertook.

We assessed methods as:

• low risk of bias (e.g. no missing outcome data; missing outcome data balanced across groups);
• high risk of bias (e.g. numbers or reasons for missing data imbalanced across groups; ‘as treated’ analysis done with substantial departure of intervention received from that assigned at randomisation);

(5) Selective reporting (checking for reporting bias)

We described for each included study how we investigated the possibility of selective outcome reporting bias and what we found.

• low risk of bias (where it is clear that all of the study’s pre‐specified outcomes and all expected outcomes of interest to the review have been reported);
• high risk of bias (where not all the study’s pre‐specified outcomes have been reported; one or more reported primary outcomes were not pre‐specified; outcomes of interest are reported incompletely and so cannot be used; study fails to include results of a key outcome that would have been expected to have been reported);

(6) Other bias (checking for bias due to problems not covered by (1) to (5) above)

We described for each included study any important concerns we had about other possible sources of bias.

(7) Overall risk of bias

We made explicit judgements about whether studies were at high risk of bias, according to the criteria given in the Handbook ( Higgins 2011 ). With reference to (1) to (6) above, we planned to assess the likely magnitude and direction of the bias and whether we considered it is likely to impact on the findings. In future updates, we will explore the impact of the level of bias through undertaking sensitivity analyses ‐ see Sensitivity analysis .

Assessment of the quality of the evidence using the GRADE approach

For this update the quality of the evidence was assessed using the GRADE approach as outlined in the GRADE handbook in order to assess the quality of the body of evidence relating to the following outcomes for the main comparison ‐ X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry in cephalic presentations.

We used the GRADEpro Guideline Development Tool to import data from Review Manager 5.3 ( RevMan 2014 ) in order to create a 'Summary of findings’ table. A summary of the intervention effect and a measure of quality for each of the above outcomes was produced using the GRADE approach. The GRADE approach uses five considerations (study limitations, consistency of effect, imprecision, indirectness and publication bias) to assess the quality of the body of evidence for each outcome. The evidence can be downgraded from 'high quality' by one level for serious (or by two levels for very serious) limitations, depending on assessments for risk of bias, indirectness of evidence, serious inconsistency, imprecision of effect estimates or potential publication bias.

Measures of treatment effect

Dichotomous data.

For dichotomous data, we presented results as summary risk ratio with 95% confidence intervals.

Continuous data

We did not include any continuous outcomes, however, if we do include them in future updates, we will use the mean difference if outcomes are measured in the same way between trials. We will use the standardised mean difference to combine trials that measure the same outcome, but use different methods.

Unit of analysis issues

Cluster‐randomised trials.

We did not identify any cluster‐randomised trials to include in the analyses. However, in future updates of the review, if we identify suitable cluster‐randomised trials, we will adjust their sample sizes or standard errors using the methods described in the Handbook Section 16.3.4 or 16.3.6 using an estimate of the intracluster correlation co‐efficient (ICC) derived from the trial (if possible), from a similar trial or from a study of a similar population. If we use ICCs from other sources, we will report this and conduct sensitivity analyses to investigate the effect of variation in the ICC. If we identify both cluster‐randomised trials and individually‐randomised trials, we plan to synthesise the relevant information. We will consider it reasonable to combine the results from both if there is little heterogeneity between the study designs and the interaction between the effect of intervention and the choice of randomisation unit is considered to be unlikely.

We will also acknowledge heterogeneity in the randomisation unit and perform a sensitivity or subgroup analysis to investigate the effects of the randomisation unit.

Cross‐over trials

Cross‐over trials were not eligible for this review.

Other unit of analysis issues

Multiple pregnancies.

Women with multiple pregnancies were not included in this review. If included in future updates, we will use cluster‐trial methods as described above to adjust the data. Babies from multiple pregnancies may be more likely to develop the same outcomes (non‐independence), so counting each as a separate data point may overestimate the sample size and make confidence intervals too narrow. We will regard each woman as a randomised cluster and use cluster‐trial methods to adjust outcomes for the baby.

Trials with more than two arms

If we had identified trials with more than two arms we would have pooled results using the methods set out in the Handbook (Higgins 2011) to avoid double‐counting.

Dealing with missing data

For included studies, levels of attrition were noted. In future updates, if more eligible studies are included, the impact of including studies with high levels of missing data in the overall assessment of treatment effect will be explored by using sensitivity analysis.

For all outcomes, analyses were carried out, as far as possible, on an intention‐to‐treat basis, i.e. we attempted to include all participants randomised to each group in the analyses. The denominator for each outcome in each trial was the number randomised minus any participants whose outcomes were known to be missing.

Assessment of heterogeneity

We assessed statistical heterogeneity in each meta‐analysis using the Tau², I² and Chi² statistics. We regarded heterogeneity as substantial if an I² was greater than 30% and either a Tau² was greater than zero, or there was a low P value (less than 0.10) in the Chi² test for heterogeneity. If we had identified substantial heterogeneity (above 30%), we would have explored it.

Assessment of reporting biases

In future updates, if there are 10 or more studies in the meta‐analysis, we will investigate reporting biases (such as publication bias) using funnel plots. We will assess funnel plot asymmetry visually. If asymmetry is suggested by a visual assessment, we will perform exploratory analyses to investigate it.

Data synthesis

We carried out statistical analysis using the Review Manager software ( RevMan 2014 ). We used fixed‐effect meta‐analysis for combining data where it was reasonable to assume that studies were estimating the same underlying treatment effect: i.e. where trials were examining the same intervention, and the trials’ populations and methods were judged sufficiently similar.

In future updates, if there is clinical heterogeneity sufficient to expect that the underlying treatment effects differed between trials, or if substantial statistical heterogeneity is detected, we will use random‐effects meta‐analysis to produce an overall summary, if an average treatment effect across trials is considered clinically meaningful. The random‐effects summary will be treated as the average range of possible treatment effects and we will discuss the clinical implications of treatment effects differing between trials. If the average treatment effect is not clinically meaningful, we will not combine trials. If we use random‐effects analyses, the results will be presented as the average treatment effect with 95% confidence intervals, and the estimates of Tau² and I².

Subgroup analysis and investigation of heterogeneity

We did not use subgroup analyses to investigate substantial heterogeneity. We carried out a clinical subgroup analyses on an issue of particular interest: women with no previous caesarean section versus women with previous caesarean section. This analysis was carried out for each review outcome. We assessed subgroup differences by interaction tests available within RevMan ( RevMan 2014 ). We reported the results of subgroup analyses quoting the Chi² statistic and P value, and the interaction test I² value.

Sensitivity analysis

We carried out sensitivity analyses to explore the effect of trial quality assessed by concealment of allocation with studies at high risk of allocation bias being excluded from the analyses in order to assess whether this makes any difference to the overall result. In future updates, if any trial is judged to be of poor quality due to being at high risk of bias for allocation concealment, high attrition rates, or both, we will also exclude these from the analysis.

Description of studies

Please see Characteristics of included studies and Characteristics of excluded studies for further details.

Results of the search

For this update, we assessed two reports of one trial ( Gaitan 2009 ) from a search of Cochrane Pregnancy and Childbirth's Trials Register (January 2017). In total, five trials are now included ( Crichton 1962 ; Gaitan 2009 ; Parsons 1985 ; Richards 1985 ; Thubisi 1993 ) and one is excluded ( Farrell 2002 ). See: Figure 1 .

Study flow diagram.

Included studies

Five trials with a total of 1159 women were included.

Study design

All included trials were two‐armed randomised controlled trials, using individual randomisation. Sample sizes were small and ranged from 102 ( Richards 1985 ) to 305 women ( Crichton 1962 ).

Trials were conducted in hospitals in South Africa ( Crichton 1962 ; Richards 1985 ; Thubisi 1993 ), USA ( Parsons 1985 ) and Spain ( Gaitan 2009 ).

Participants

Gaitan 2009 and Parsons 1985 only included nulliparous women in their trials, Crichton 1962 did not specify the parity of the women included, and Richards 1985 and Thubisi 1993 only included women with one previous lower segment caesarean section.

Gaitan 2009 and Parsons 1985 only randomised women who were being induced or augmented with oxytocin. Crichton 1962 randomised women when they were in labour and their doctor requested a pelvimetry. Both Richards 1985 and Thubisi 1993 performed pelvimetry at 36 weeks' gestation so women were randomised during pregnancy.

Interventions and comparisons

All of the trials included in the review examined X‐ray pelvimetry. We did not identify any trials comparing clinical pelvimetry with no pelvimetry, or examining other types of radiological pelvimetry.

Crichton 1962 included 305 women in labour whose attending doctors requested pelvimetry. Women were randomised to receive X‐ray pelvimetry or no pelvimetry during labour. No fetal heart rate monitoring was performed.

Parsons 1985 recruited 200 primigravid women who required induction of labour or augmentation of labour with oxytocin. All women received a clinical pelvimetry. Women were subsequently randomised by hospital number to either receive or not receive an X‐ray pelvimetry. Continuous fetal heart rate monitoring was done.

Richards 1985 included 102 women with one previous caesarean section (classical uterine incision being excluded). Women were randomised into two groups: the first group received an X‐ray pelvimetry at 36 weeks' gestation. If the pelvic inlet was less than 10.5 cm in the antero‐posterior diameter or less than 11.5 cm in the transverse diameter, an elective caesarean section was performed. The other women and the control group underwent a trial of scar, and had X‐ray pelvimetry postpartum as a comparison.

Thubisi 1993 randomised 288 women with one previous transverse lower segment caesarean section. The intervention group received an X‐ray pelvimetry at 36 weeks' gestation. A sagittal inlet of less than 11 cm, sagittal outlet of less than 10 cm, transverse inlet less than 11.5 cm, and transverse outlet (bispinous) less than 9 cm was an indication for caesarean section. The other women in the intervention group and the control group awaited a trial of scar.

Gaitan 2009 included 264 women. Women were randomised into two groups to either receive or not receive an X‐ray pelvimetry.

Crichton 1962 : outcomes were caesarean section/symphysiotomy, perinatal mortality, asphyxia and maternal survival.

Parsons 1985 : outcomes assessed were length of labour, length of rupture of membranes, length of oxytocin administration, type of birth, Apgar scores and birthweight.

Richards 1985 : outcomes measured were mode of birth, pelvimetry measurements, birthweight and average stay in hospital.

Thubisi 1993 : outcomes measured were caesarean section, perinatal mortality, birthweight, scar dehiscence, puerperal pyrexia, wound sepsis and blood transfusion.

Gaitan 2009 : outcomes measured were time from induction to birth of baby, method of birth, use of instruments during birth, any adverse effects and perinatal mortality.

Funding sources were not disclosed by any of the trialists.

Excluded studies

One trial was excluded: Farrell 2002 ; there were too few women recruited, study protocol was not adhered to, and the trial was stopped prior to completion due to inadequate randomisation.

Risk of bias in included studies

Please see Figure 2 and Figure 3 for a summary of 'Risk of bias' assessments.

'Risk of bias' summary: review authors' judgements about each risk of bias item for each included study.

'Risk of bias' graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

In all studies selection bias cannot be excluded, although Richards 1985 and Thubisi 1993 randomised a more homogeneous group of women as they were not in labour at the time of randomisation.

Both Crichton 1962 and Richards 1985 risk of selection bias was assessed as being 'unclear' due to not enough information being provided in the papers. Parsons 1985 and Thubisi 1993 were assessed as high risk as Parsons 1985 allocated women by hospital number, and Thubisi 1993 'randomly' assigned women at the first antenatal visit to one of two consultant teams, allocated by admitting clerks who had no medical training and knowledge of how they would be managed. Gaitan 2009 used a random number table to allocate women into groups but allocation concealment is not mentioned adequately.

Crichton 1962 relied on the attending clinician to request a pelvimetry and Parsons 1985 included a group of women requiring augmentation of labour, indicating that labour was already not progressing as expected.

None of the trials blinded participants, care givers or outcome assessors. For this type of outcome, blinded would be very difficult.

Incomplete outcome data

Thubisi 1993 randomised 306 women but only followed up 288. This loss to follow‐up is relatively low but loss of two women in the pelvimetry group related to outcomes of the study (women opted for caesarean section). For this reason, Thubisi 1993 was assessed as being at unclear risk of attrition bias. Richards 1985 was also assessed as unclear due to missing totals in the results tables of the study.

All remaining trials were assessed to be at low risk of attrition bias as data were reported for all women who were randomised.

Selective reporting

Protocols were not available for any of the included studies. Crichton 1962 , Parsons 1985 , Richards 1985 and Thubisi 1993 did not pre‐specify outcomes in the methods text. Gaitan 2009 does not report all outcomes, however in is unclear if this is due to translation issues. All trials were assessed to be at unclear risk of reporting bias.

Other potential sources of bias

All the trials were assessed to be at unclear risk of other bias except for Parsons 1985 and Thubisi 1993 who were assessed to be at low risk of bias as the baseline characteristics of both groups were similar and there was no other evidence of bias. Crichton 1962 and Richards 1985 did not report any baseline characteristics, and Gaitan 2009 had some unclear discrepancy between totals in tables and in text though it was unclear if this were due to translation issues.

Effects of interventions

See: Table 1

Summary of findings 1

1 Most studies contributing data had design limitations. Two studies had serious design limitations (high risk of bias for sequence generation and allocation concealment) one of which contributed 37.4% of weight (‐2).

2 Most studies contributing data had design limitations. (‐1)

3 Wide confidence interval crossing the line of no effect, small sample size, few events and lack of precision. (‐2)

4 One study contributing data with serious design limitations. (‐2)

5 Very wide confidence intervals crossing the line of no effect, small sample size and few events. (‐2)

6 Study contributing 79.7% total weight has serious design limitations. (‐2)

X‐ray pelvimetry versus no X‐ray pelvimetry

All five trials assessed the rate of caesarean section as an outcome, including a total of 1159 women. Crichton 1962 reported caesarean section and symphysiotomy results combined, therefore data for both caesarean section and symphysiotomy are included in this analysis. No other study reported symphysiotomy.

Women who had X‐ray pelvimetry had a higher rate of caesarean section than those women who had no X‐ray pelvimetry. The risk ratio (RR) for caesarean section is 1.34 (95% confidence interval (CI) 1.19 to 1.52; 1159 women; 5 trials; low‐quality evidence ) Analysis 1.1 when compared to women who did not get an X‐ray pelvimetry. Quality of evidence as assessed using GRADE is low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 1: Caesarean section

Subgroup interaction tests suggest no clear differences in effects for women with previous versus women with no previous caesarean section (Test for subgroup differences: Chi² = 1.52, df = 1 (P = 0.22), I² = 34.1%). The two trials that only included women with a previous section ( Richards 1985 ; Thubisi 1993 ), performed elective caesarean sections on the women whose pelvic inlets did not satisfy pre‐specified requirements following antenatal X‐ray pelvimetry; all those who did satisfy requirements were left to go into spontaneous labour. A higher caesarean rate might therefore be expected. In future updates of this review it will be useful to analyse data for rates of elective and emergency caesarean sections separately.

All five trials assessed the perinatal mortality as an outcome, including a total of 1159 women. There is no clear difference in perinatal mortality between women who did and women who did not receive an X‐ray pelvimetry (RR 0.53, 95% CI 0.19 to 1.45; 1159 infants; 5 trials; very low‐quality evidence ) Analysis 1.2 . Quality of evidence as assessed using GRADE is very low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 2: Perinatal mortality

One trial including 288 women who all had a previous caesarean ( Thubisi 1993 ) assessed the incidence of puerperal pyrexia as an outcome after caesarean in both groups (women who did receive an X‐ray pelvimetry compared to women who did not). Little difference was found: RR 0.80 (95% CI 0.22 to 2.92; 288 women; 1 trial) Analysis 1.3 .

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 3: Puerperal pyrexia

One trial including 288 women ( Thubisi 1993 ) assessed the incidence of wound sepsis as an outcome after caesarean in both groups (women who did receive an X‐ray pelvimetry compared to women who did not). Little difference was found: RR 0.83 (95% CI 0.26 to 2.67; 288 women; 1 trial; very low‐quality evidence ) Analysis 1.4 . Quality of evidence as assessed using GRADE is very low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 4: Wound sepsis

One trial including 288 women ( Thubisi 1993 ) assessed the need for blood transfusion as an outcome in both groups (women who did receive an X‐ray pelvimetry compared to women who did not). No difference was found: RR 1.00 (95% CI 0.39 to 2.59; 288 women; 1 trial; very low‐quality evidence ) Analysis 1.5 . Quality of evidence as assessed using GRADE is very low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 5: Blood transfusion

Two trials including 390 women ( Richards 1985 ; Thubisi 1993 ) assessed the incidence of scar dehiscence as an outcome in women who had one previous transverse uterine segment caesarean section and underwent trial of scar. Little difference was found: RR 0.59 (95% CI 0.14 to 2.46; 390 women; 2 trials; v ery low‐quality evidence ) Analysis 1.6 . Quality of evidence as assessed using GRADE is very low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 6: Scar dehiscence

One trial including 305 infants ( Crichton 1962 ) assessed incidence of perinatal asphyxia. Little difference was found: RR 0.66 (95% CI 0.39 to 1.10; 305 infants; 1 trial) Analysis 1.7 .

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 7: Perinatal asphyxia

Admission to special care baby unit

One trial including 288 infants ( Thubisi 1993 ) assessed the need for admission to a special care baby unit. Little difference was found: RR 0.20 (95% CI 0.01 to 4.13; 288 infants; 1 trial; very low‐quality evidence ) Analysis 1.8 . Quality of evidence as assessed using GRADE is very low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 8: Admission to special care baby units

No trials assessed the Apgar score less than seven at five minutes as an outcome.

Women without previous caesarean section

Three trials included women with no previous caesarean section ( Crichton 1962 ; Gaitan 2009 ; Parsons 1985 ) with a total number of 769 women. There is a higher caesarean section rate (and symphysiotomy rate in Crichton 1962 ) in the X‐ray pelvimetry group (RR 1.24, 95% CI 1.02 to 1.52; 769 women; 3 trials). There is no difference in perinatal mortality (RR 0.64, 95% CI 0.21 to 1.90; 769 women; 3 trials). There was a slight decrease in perinatal asphyxia and perinatal mortality in Crichton 1962 , but this decrease in perinatal mortality was not observed in Parsons 1985 or Gaitan 2009 . Neither trial reported perinatal asphyxia. The decrease seen in Crichton 1962 could be due to chance or lack in fetal monitoring. None of these trials reported puerperal pyrexia, wound sepsis, blood transfusion, or admission to special care baby unit. Scar dehiscence was not relevant to these women.

Women with previous caesarean section

Two trials included women who had a previous transverse lower segment caesarean section ( Richards 1985 ; Thubisi 1993 ), with a total number of 390 women. There was an overall increase in the caesarean section rate in both studies in the X‐ray pelvimetry groups (RR 1.45, 95% CI 1.26 to 1.67; 390 women; 2 trials). There was a slight decrease in perinatal mortality, which could have occurred by chance, in Richards 1985 , but this was not observed in Thubisi 1993 where there were no perinatal deaths in either group (RR 0.19, 95% CI 0.01 to 3.91; 390 women; 2 trials). There were similar rates of scar dehiscence in the intervention and control groups (RR 0.59, 95% CI 0.14 to 2.46; 390 women; 2 trials). Thubisi 1993 reported a slight increase in admissions to special care baby units in the control group, but again these could have occurred by chance. Richards 1985 did not report this outcome. Only Thubisi 1993 reported puerperal pyrexia, wound sepsis and blood transfusion and did not find any difference between the groups.

We carried out sensitivity analysis for lack of allocation concealment. Parsons 1985 and Thubisi 1993 were assessed to be at high risk of selection bias and were removed from Analysis 1.1 : Caesarean section/symphysiotomy and Analysis 1.2 : Perinatal mortality. There were not sufficient data to remove these trials from the other outcomes and maintain a meaningful analysis.

For the outcome caesarean section/symphysiotomy, removing the trial data widened the CIs and lessened the effect slightly (RR 1.25, 95% CI 1.04 to 1.49), but the data still showed that women who had pelvimetry were more likely to have a caesarean section. Regarding the women without a previous caesarean section, removing Parsons 1985 meant that the CIs crossed the line of no effect (RR 1.19, 95% CI 0.96 to 1.47).

There were no perinatal deaths in either Parsons 1985 or Thubisi 1993 , so removing the data from the meta‐analysis made no difference to the overall relative risk.

X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that used other types of pelvimetry (other radiological examination).

Summary of main results

Five trials with a total of 1159 women were included. All used X‐ray pelvimetry to assess the pelvis. X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that used other types or pelvimetry.

Women who received an X‐ray pelvimetry, had a higher risk having a caesarean section, without a decrease in perinatal mortality. The control groups tended to a slightly raised perinatal mortality, but this could be due to chance. The numbers studied were insufficient to assess perinatal mortality adequately. No clear differences were found between groups for puerperal pyrexia, wound sepsis, blood transfusion, scar dehiscence, perinatal asphyxia or admission to special care baby unit. No trial reported Apgar score less than seven at five minutes.

Parsons 1985 explains the increased perinatal mortality and asphyxia in Crichton 1962 by the lack of electronic fetal monitoring available to the women in Crichton's trial. The two deaths in the study of Richards 1985 occurred in utero before the onset of labour.

Some of the outcomes in this review, relating to women with a previous caesarean, are difficult to interpret because they are mediated by another outcome, for example, wound sepsis and blood transfusion are only relevant to those women who have a caesarean section.

Overall completeness and applicability of evidence

The trials are compatible with respect to the common measures of outcome. The small number of trials included in this review address the research question and do not support the use of X‐ray pelvimetry, though they are of low quality, and there are no trials to assess the use of computed tomography (CT) or magnetic resonance imaging (MRI) pelvimetry. The paucity of trials assessing the effectiveness of all methods of pelvimetry, for both women with and without a previous caesarean, limits the applicability of this review. The majority of the few trials available are over 20 years old. This perhaps reflects how little pelvimetry is used by clinicians in current practice.

The trials were also conducted in a small number of countries (South Africa, Spain, and the USA) and therefore the findings may not be applicable to low‐income settings.

Quality of the evidence

All trial designs regarding treatment allocation were of poor quality, assessed as high or unclear risk of bias. None of the trials blinded participants, staff or outcome assessors. The trials were not well‐reported so it was difficult to assess the other 'Risk of bias' domains. The two trials in women with previous caesarean sections were performed at the same institution a few years apart. We have found that overall, the findings are at a moderate to high risk of bias. Please see Figure 2 for a summary of the risk of bias.

We used GRADEpro software to grade evidence for our selected outcomes; for caesarean section we rated the evidence low quality and all the other outcomes, perinatal mortality, wound sepsis, blood transfusion, scar dehiscence and admission to special care baby unit as very low quality. Downgrading was due to risk of bias relating to lack of allocation concealment and blinding, and imprecision of effect estimates. Please see Table 1 .

Potential biases in the review process

We took steps to reduce bias as we are aware of the potential to introduce bias throughout the process of writing the review. Two review authors assessed each study for possible inclusion, assessed the quality of the trials and extracted data independently. We recognise that assessing the quality of the trials can be subjective and that different people assessing risk of bias may have come up with different judgements.

Agreements and disagreements with other studies or reviews

The results of this review agree with another non‐Cochrane systematic review that looked at clinical interventions, including X‐ray pelvimetry, which increased vaginal birth after caesarean section (VBAC) ( Catling‐Paull 2011 ). Catling‐Paull 2011 found that X‐ray pelvimetry was a poor predictor of birth outcome, and that women who received pelvimetry were less likely to attempt a vaginal birth. Subsequently, the caesarean section rate was higher in the groups where women had pelvimetry.

Implications for practice

X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that used other types or pelvimetry (e.g. other radiological examinations). There is not enough evidence to support the use of X‐ray pelvimetry for deciding on the mode of delivery in women whose fetuses have a cephalic presentation, and the practice may be harmful to the mother by increasing the risk of having a caesarean section, without increasing the benefit to the fetus or neonate.

Implications for research

Further research should be directed towards defining whether there are specific clinical situations, for example, breech presentations, in which X‐ray pelvimetry can be shown to be of value. Newer methods of pelvimetry should be subjected to randomised trials to assess their value.

Further trials of X‐ray pelvimetry in cephalic presentations would be of value if large enough to assess the effect on perinatal mortality.

Anthony Todd, December 2020

It occurred to me that, having been involved with dogs with large heads and tiny pelvices that a simple measurement of the widest part of the pelvis may be related to the chances of dystocia. A basic measurement at any stage of pregnancy. or before. may predict with some, not all, as exceptions in nature are the rule, accuracy the chances of dystocia. these women could therefore be identified and prepared [in all sorts of ways] for the likelihood of dystocia.

Protocol first published: Issue 2, 1997 Review first published: Issue 2, 1997

Acknowledgements

Professor Justus Hofmeyr and Ms Cheryl Nikodem for assisting me with the study and teaching me (V Vannevel) the use of Review Manager. Thanks to Therese Dowswell (Cochrane Pregnancy and Childbirth) for her contribution in assessing studies and help preparing the 'Summary of findings' table for this update (2016).

This research was supported by a grant from the Department of Reproductive Health and Research, World Health Organization (WHO). The findings, interpretations and conclusions expressed in this paper are entirely those of the authors and should not be attributed in any manner whatsoever to WHO.

We thank El‐Marie Farrell for contributions to the previous update.

As part of the pre‐publication editorial process, this review has been commented on by three peers (an editor and two referees who are external to the editorial team), a member of Cochrane Pregnancy and Childbirth's international panel of consumers and the Group's Statistical Adviser.

This project was supported by the National Institute for Health Research, via Cochrane Infrastructure funding to Cochrane Pregnancy and Childbirth. The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the Systematic Reviews Programme, NIHR, NHS or the Department of Health.

Edited (no change to conclusions)

Data and analyses

Comparison 1, characteristics of studies, characteristics of included studies [ordered by study id], characteristics of excluded studies [ordered by study id], differences between protocol and review.

Title: We changed the title from Pelvimetry for fetal cephalic presentations at or near term to Pelvimetry for fetal cephalic presentations at or near term for deciding on mode of delivery .

Objectives: We removed assessing the effects of postnatal pelvimetry from the objectives as this could not impact on mode of delivery.

We also removed the following hypothesis.

• Information provided by pelvimetry in women without previous caesarean section is useful because it decreases the morbidity and mortality in the women and fetuses or neonates.
• Information provided by pelvimetry in women with previous caesarean section is useful because it decreases the morbidity and mortality in the women and fetuses or neonates.

We have clarified aspects in the section on Criteria for considering studies for this review, as follows:

All acceptably randomised comparisons of the use of pelvimetry in cephalic presentations in:

• women without previous caesarean section;
• women with previous caesarean section.

has changed to:

• Women without caesarean section;
• Women with previous caesarean section.

Pregnant women with singleton, cephalic presentation fetus who have or have not had a previous caesarean section. Studies which recruited women before, or during labour were included as well as women for spontaneous labour, induction or trial of scar after previous caesarean section.

Policy of elective caesarean section or trial of labour or scar depending on the prediction of pelvimetry as opposed to trial of labour or scar in all.

Outcomes: We changed ' Caesarean section/symphysiotomy' to ' Caesarean section'. Crichton 1962 only, reported the composite outcome of caesarean section/symphysiotomy, and did not report data for these outcomes separately. It is not clear how many symphysiotomies were performed in this trial and we could not report the data as two separate outcomes. We have documented this in the results section and in footnotes in Analysis 1.1 .

'Summary of findings' table: We assessed the trial quality by using GRADE assessment. This is documented in Table 1 .

Contributions of authors

V Vannevel assisted RC Pattinson with the 2016 update. V Vannevel analysed and interpreted the results, and prepared the update. A Cuthbert assessed studies for inclusion and prepared the 'Summary of findings' table.

Sources of support

Internal sources.

• University of Pretoria, South Africa

External sources

• South African Medical Research Council, South Africa
• Department of Reproductive Health and Research, World Health Organization, Switzerland
• UNDP‐UNFPA‐UNICEF‐WHO‐World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP), Department of Reproductive Health and Research (RHR), World Health Organization, Switzerland

Declarations of interest

Robert C Pattinson: no conflict of interest. Anna Cuthbert: no conflict of interest. Valerie Vannevel: no conflict of interest.

References to studies included in this review

Crichton 1962 {published data only}.

• Crichton D. The accuracy and value of cephalopelvimetry . Journal of Obstetrics and Gynaecology of the British Commonwealth 1962; 69 :366-78. [ Google Scholar ]

Gaitan 2009 {published data only}

• Gaitan N, Duenas JL, Bedoya C, Taboada C, Polo J. Prospective, randomised and controlled study to evaluate the usefulness of radiopelvimetry in induced labour in primigravidae [Estudio prospectivo, aleatorizado y controlado para evaluar la utilidad de la radiopelvimetria en la induccion de parto en primigravidas]. Progresos de Obstetricia y Ginecologia 2009; 52 ( 10 ):552-6. [ Google Scholar ]
• Gaitan Quintero N, Duenas Diez JL, Bedoya Bergua C, Taboada Montes C, Padillo JP. The use of the radiopelvimetria previously to the induction of labor in primigravidas . Journal of Maternal-Fetal and Neonatal Medicine 2010; 23 ( S1 ):278. [ Google Scholar ]

Parsons 1985 {published data only}

• Parsons MT, Spellacy WN. Prospective randomised study of X-ray pelvimetry in the primigravida . Obstetrics & Gynecology 1985; 66 :76-9. [ PubMed ] [ Google Scholar ]

Richards 1985 {published data only}

• Richards A, Strang A, Moodley J, Philpott H. Vaginal delivery following caesarean section - is X-ray pelvimetry a reliable predictor? In: Proceedings of 4th Conference on Priorities in Perinatal Care in South Africa, 1985; Natal, South Africa . 1985:62-5.

Thubisi 1993 {published data only}

• Thubisi M, Ebrahim A, Moodley J, Shweni PM. Vaginal delivery after previous caesarean section: is X-ray pelvimetry necessary? British Journal of Obstetrics and Gynaecology 1993; 100 :421-4. [ PubMed ] [ Google Scholar ]

References to studies excluded from this review

Farrell 2002 {unpublished data only}.

• Volschenk S, Farrell E, Jeffery BS, Pattinson RC. Clinical pelvimetry as a predictor of vaginal delivery in women with one previous caesarean section . In: 20th Conference on Priorities in Perinatal Care in Southern Africa; 2001 March 6-9; KwaZulu-Natal, South Africa . 2002.

Additional references

Catling‐paull 2011.

• Catling-Paull C, Johnston R, Ryan C, Foureur MJ, Homer CSE. Clinical interventions that increase the uptake and success of vaginal birth after caesarean section: a systematic review . Journal of Advanced Nursing 2011; 67 ( 8 ):1646-61. [ PubMed ] [ Google Scholar ]
• Dodd JM, Crowther CA, Huertas E, Guise JM, Horey D. Planned elective repeat caesarean section versus planned vaginal birth for women with a previous caesarean birth . Cochrane Database of Systematic Reviews 2013, Issue 12 . Art. No: CD004224. [DOI: 10.1002/14651858.CD004224.pub3] [ PubMed ] [ CrossRef ] [ Google Scholar ]

Higgins 2011

• Higgins JPT, Green S, editors. Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011 . Available from www.cochrane-handbook.org .

Mengert 1948

• Mengert WF. Estimation of pelvic capacity . JAMA 1948; 138 :169-74. [ PubMed ] [ Google Scholar ]

Morgan 1992

• Morgan MA, Thurnau GR. Efficacy of the fetal-pelvic index in nulliparous women at high risk for fetal-pelvic disproportion . American Journal of Obstetrics and Gynecology 1992; 166 ( 3 ):810-4. [ PubMed ] [ Google Scholar ]

Morris 1993

• Morris CW, Heggie JCP, Acton CM. Computed tomography pelvimetry: accuracy and radiation dose compared with conventional pelvimetry . Australasian Radiology 1993; 37 :186-91. [ PubMed ] [ Google Scholar ]

RevMan 2014 [Computer program]

• The Nordic Cochrane Centre, The Cochrane Collaboration Review Manager (RevMan) . Version 5.3. Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2014.

Sporri 2002

• Sporri S, Thoeny HC, Raio L, Lachat R, Vock P, Schneider H. MR imaging pelvimetry: a useful adjunct in the treatment of women at risk for dystocia? American Journal of Roentgenology 2002; 179 :137-44. [ PubMed ] [ Google Scholar ]

van Ham 1997

• Ham MAEC, Dongen PWJ, Mulder J. Maternal consequences of caesarean section - A retrospective study of intra-operative and postoperative maternal complications of caesarean section during a 10-year period . European Journal of Obstetrics & Gynecology and Reproductive Biology 1997; 74 :1-6. [ PubMed ] [ Google Scholar ]

References to other published versions of this review

Pattinson 1997.

• Pattinson RC, Farrell EME. Pelvimetry for fetal cephalic presentations at or near term . Cochrane Database of Systematic Reviews 1997, Issue 2 . Art. No: CD000161. [DOI: 10.1002/14651858.CD000161] [ PubMed ] [ CrossRef ] [ Google Scholar ]

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Delivery presentations

Cephalic (head first) presentation is considered normal, but a breech (feet or buttocks first) delivery can be very difficult, even dangerous for the mother and the baby.

Review Date 11/10/2022

Updated by: John D. Jacobson, MD, Department of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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Normal Labor and Delivery

Key Abbreviations American Academy of Pediatrics AAP American College of Obstetricians and Gynecologists ACOG Body mass index BMI California Maternal Quality Care Collaborative CMQCC Cephalopelvic disproportion CPD Cervical length CL Computed tomography CT Dehydroepiandrosterone sulfate DHEAS Fetal heart rate FHR Intrauterine pressure catheter IUPC Intraventricular hemorrhage IVH Left occiput anterior LOA Magnetic resonance imaging MRI Montevideo unit MVU Normal saline NS Occiput anterior OA Occiput posterior OP Occiput transverse OT Prostaglandin PG Randomized controlled trial RCT Right occiput anterior ROA Skin-to-skin contact SSC Society for Maternal-Fetal Medicine SMFM Overview The initiation of normal labor at term requires endocrine, paracrine, and autocrine signaling between the fetus, uterus, placenta, and the mother. Although the exact trigger for human labor at term remains unknown, it is believed to involve conversion of fetal dehydroepiandrosterone sulfate (DHEAS) to estriol and estradiol by the placenta. These hormones upregulate transcription of progesterone, progesterone receptors, oxytocin receptors, and gap junction proteins within the uterus, which helps to facilitate regular uterine contractions. The latent phase of labor is characterized by a slower rate of cervical dilation, whereas the active phase of labor is characterized by a faster rate of cervical dilation and does not begin for most women until the cervix is dilated 6 cm. The duration of the second stage of labor can be affected by a number of factors including epidural use, fetal position, fetal weight, ethnicity, and parity. This chapter will review the characteristics and physiology of normal labor at term. Factors that affect the average duration of the first and second stage of labor progress will be reviewed, and an evidence-based evaluation of strategies to support the mother during labor and facilitate safe delivery of the fetus will be presented. Labor: Definition and Physiology Labor is defined as the process by which the fetus is expelled from the uterus. More specifically, labor requires regular, effective contractions that lead to dilation and effacement of the cervix. This chapter describes the physiology and normal characteristics of term labor and delivery. The physiology of labor initiation has not been completely elucidated, but the putative mechanisms have been well reviewed by Liao and colleagues. Labor initiation is species specific, and the mechanisms of human labor are unique. The four phases of labor from quiescence to involution are outlined in Figure 12-1 . The first phase is quiescence, which represents that time in utero before labor begins, when uterine activity is suppressed by the action of progesterone, prostacyclin, relaxin, nitric oxide, parathyroid hormone–related peptide, and possibly other hormones. During the activation phase , estrogen begins to facilitate expression of myometrial receptors for prostaglandins (PGs) and oxytocin, which results in ion channel activation and increased gap junctions. This increase in the gap junctions between myometrial cells facilitates effective contractions. In essence, the activation phase readies the uterus for the subsequent stimulation phase , when uterotonics—particularly PGs and oxytocin—stimulate regular contractions. In the human, this process at term may be protracted, occurring over days to weeks. The final phase, uterine involution , occurs after delivery and is mediated primarily by oxytocin. The first three phases of labor require endocrine, paracrine, and autocrine interaction between the fetus, membranes, placenta, and mother. FIG 12-1 Regulation of uterine activity during pregnancy and labor. (Modified from Challis JRG, Gibb W. Control of parturition. Prenat Neonat Med. 1996;1:283.) The fetus has a central role in the initiation of term labor in nonhuman mammals; in humans, the fetal role is not completely understood ( Fig. 12-2 ). In sheep, term labor is initiated through activation of the fetal hypothalamic-pituitary-adrenal (HPA) axis, with a resultant increase in fetal adrenocorticotropic hormone (ACTH) and cortisol. Fetal cortisol increases production of estradiol and decreases production of progesterone by a shift in placental metabolism of cortisol dependent on placental 17α-hydroxylase. The change in the circulating progesterone/estradiol concentration stimulates placental production of oxytocin and PG, particularly PGF 2α , which in turn promotes myometrial contractility. If this increase in fetal ACTH and cortisol is blocked, progesterone levels remain unchanged, and parturition is delayed. In contrast, humans lack placental 17α-hydroxylase, maternal and fetal levels of progesterone remain elevated, and no trigger exists for parturition because of an increase in fetal cortisol near term. Rather, in humans, evidence suggests that placental production of corticotropin-releasing hormone (CRH) near term activates the fetal hypothalamic-pituitary axis and results in increased production of dehydroepiandrostenedione by the fetal adrenal gland. Fetal dehydroepiandrostenedione is converted in the placenta to estradiol and estriol. Placenta-derived estriol potentiates uterine activity by enhanc­ing the transcription of maternal (likely decidual) PGF 2α , PG receptors, oxytocin receptors, and gap-junction proteins. In humans, no documented decrease in progesterone has been observed near term, and a fall in progesterone is not necessary for labor initiation. However, some research suggests the possibility of a functional progesterone withdrawal in humans. Labor is accompanied by a decrease in the concentration of progesterone receptors and a change in the ratio of progesterone receptor isoforms A and B in both the myometrium and the membranes. During labor, increased expression of nuclear and membrane progesterone receptor isoforms serve to enhance genomic expression of contraction-associated proteins, increase intracellular calcium, and decrease cyclic adenosine monophosphate (cAMP). More research is needed to elucidate the precise mechanism through which the human parturition cascade is activated. Fetal maturation might play an important role as might maternal cues that affect circadian cycling. Most species have distinct diurnal patterns of contractions and delivery, and in humans, the majority of contractions occur at night. FIG 12-2 Proposed “parturition cascade” for labor induction at term. The spontaneous induction of labor at term in the human is regulated by a series of paracrine/autocrine hormones acting in an integrated parturition cascade responsible for promoting uterine contractions. PGE 2 , prostaglandin E 2 ; PGEM, 13,14-dihydro-15-keto-PGE 2 ; PGF 2α , prostaglandin F 2α ; PGFM, 13, 14-dihydro-15keto-PGF 2α . (Modified from Norwitz ER, Robinson JN, Repke JT. The initiation of parturition: a comparative analysis across the species. Curr Prob Obstet Gynecol Fertil. 1999;22:41.) Oxytocin is commonly used for labor induction and augmentation, and a full understanding of the mechanism of oxytocin action is important. Oxytocin is a peptide hormone synthesized in the hypothalamus and released from the posterior pituitary in a pulsatile fashion. At term, oxytocin serves as a potent uterotonic agent capable of stimulating uterine contractions at intravenous (IV) infusion rates of 1 to 2 mIU/min. Oxytocin is inactivated largely in the liver and kidney, and during pregnancy, it is degraded primarily by placental oxytocinase. Its biologic half-life is approximately 3 to 4 minutes, but it appears to be shorter when higher doses are infused. Concentrations of oxytocin in the maternal circulation do not change significantly during pregnancy or before the onset of labor, but they do rise late in the second stage of labor. Studies of fetal pituitary oxytocin production and the umbilical arteriovenous differences in plasma oxytocin strongly suggest that the fetus secretes oxytocin that reaches the maternal side of the placenta. The calculated rate of active oxytocin secretion from the fetus increases from a baseline of 1 mIU/min before labor to around 3 mIU/min after spontaneous labor. Significant differences in myometrial oxytocin receptor distribution have been reported, with large numbers of fundal receptors and fewer receptors in the lower uterine segment and cervix. Myometrial oxytocin receptors increase on average by 100- to 200-fold during pregnancy and reach a maximum during early labor. This rise in receptor concentration is paralleled by an increase in uterine sensitivity to circulating oxytocin. Specific high-affinity oxytocin receptors have also been isolated from human amnion and decidua parietalis but not decidua vera. It has been suggested that oxytocin plays a dual role in parturition. First, through its receptor, oxytocin directly stimulates uterine contractions. Second, oxytocin may act indirectly by stimulating the amnion and decidua to produce PG. Indeed, even when uterine contractions are adequate, induction of labor at term is successful only when oxytocin infusion is associated with an increase in PGF production. Oxytocin binding to its receptor activates phospholipase C. In turn, phospholipase C increases intracellular calcium both by stimulating the release of intracellular calcium and by promoting the influx of extracellular calcium. Oxytocin stimulation of phospholipase C can be inhibited by increased levels of cAMP. Increased calcium levels stimulate the calmodulin-mediated activation of myosin light-chain kinase. Oxytocin may also stimulate uterine contractions via a calcium-independent pathway by inhibiting myosin phosphatase, which in turn increases myosin phosphorylation. These pathways (of PGF 2α and intracellular calcium) have been the target of multiple tocolytic agents: indomethacin, calcium channel blockers, β-mimetics (through stimulation of cAMP), and magnesium. Mechanics of Labor Labor and delivery are not passive processes in which uterine contractions push a rigid object through a fixed aperture. The ability of the fetus to successfully negotiate the pelvis during labor and delivery depends on the complex interactions of three variables: uterine activity, the fetus, and the maternal pelvis. This complex relationship has been simplified in the mnemonic powers, passenger, passage . Uterine Activity (Powers) The powers refer to the forces generated by the uterine musculature. Uterine activity is characterized by the frequency, amplitude (intensity), and duration of contractions. Assessment of uterine activity may include simple observation, manual palpation, external objective assessment techniques (such as external tocodynamometry), and direct measurement via an intrauterine pressure catheter (IUPC). External tocodynamometry measures the change in shape of the abdominal wall as a function of uterine contractions and, as such, is qualitative rather than quantitative. Although it permits graphic display of uterine activity and allows for accurate correlation of fetal heart rate (FHR) patterns with uterine activity, external tocodynamometry does not allow measurement of contraction intensity or basal intrauterine tone. The most precise method for determination of uterine activity is the direct measurement of intrauterine pressure with an IUPC . However, this procedure should not be performed unless indicated given the small but finite associated risks of uterine perforation, placental disruption, and intrauterine infection. Despite technologic improvements, the definition of “adequate” uterine activity during labor remains unclear. Classically, three to five contractions in 10 minutes has been used to define adequate labor; this pattern has been observed in approximately 95% of women in spontaneous labor. In labor, patients usually contract every 2 to 5 minutes, with contractions becoming as frequent as every 2 to 3 minutes in late active labor and during the second stage. Abnormal uterine activity can also be observed either spontaneously or as a result of iatrogenic interventions. Tachysystole is defined as more than five contractions in 10 minutes averaged over 30 minutes. If tachysytole occurs, documentation should note the presence or absence of FHR decelerations. The term hyperstimulation should no longer be used. Various units of measure have been devised to objectively quantify uterine activity, the most common of which is the Montevideo unit (MVU) , a measure of average frequency and amplitude above basal tone (the average strength of contractions in millimeters of mercury multiplied by the number of contractions per 10 min). Although 150 to 350 MVU has been described for adequate labor, 200 to 250 MVU is commonly accepted to define adequate labor in the active phase. No data identify adequate forces during latent labor. Although it is generally believed that optimal uterine contractions are associated with an increased likelihood of vaginal delivery, data are limited to support this assumption. If uterine contractions are “adequate” to effect vaginal delivery, one of two things will happen: either the cervix will efface and dilate, and the fetal head will descend, or caput succedaneum (scalp edema) and molding of the fetal head (overlapping of the skull bones) will worsen without cervical effacement and dilation. The latter situation suggests the presence of cephalopelvic disproportion (CPD), which can be either absolute , in which the fetus is simply too large to negotiate the pelvis, or relative , in which delivery of the fetus through the pelvis would be possible under optimal conditions but is precluded by malposition or abnormal attitude of the fetal head. Fetus (Passenger) The passenger, of course, is the fetus. Several fetal variables influence the course of labor and delivery. Fetal size can be estimated clinically by abdominal palpation or ultrasound or by asking a multiparous patient about her best estimate, but all of these methods are subject to a large degree of error. Fetal macrosomia is defined by the American College of Obstetricians and Gynecologists (ACOG) as birthweight greater than or equal to the 90th percentile for a given gestational age or greater than 4500 g for any gestational age, and it is associated with an increased likelihood of planned cesarean delivery, labor dystocia, cesarean delivery after a failed trial of labor, shoulder dystocia, and birth trauma. Fetal lie refers to the longitudinal axis of the fetus relative to the longitudinal axis of the uterus. Fetal lie can be longitudinal, transverse, or oblique ( Fig. 12-3 ). In a singleton pregnancy, only fetuses in a longitudinal lie can be safely delivered vaginally. FIG 12-3 Examples of fetal lie. Presentation refers to the fetal part that directly overlies the pelvic inlet. In a fetus presenting in the longitudinal lie, the presentation can be cephalic (vertex) or breech. Compound presentation refers to the presence of more than one fetal part overlying the pelvic inlet, such as a fetal hand and the vertex. Funic presentation refers to presentation of the umbilical cord and is rare at term. In a cephalic fetus, the presentation is classified according to the leading bony landmark of the skull, which can be either the occiput (vertex), the chin (mentum), or the brow ( Fig. 12-4 ). Malpresentation , a term that refers to any presentation other than vertex, is seen in approximately 5% of all term labors (see Chapter 17 ). FIG 12-4 Landmarks of fetal skull for determination of fetal position. Attitude refers to the position of the head with regard to the fetal spine (the degree of flexion and/or extension of the fetal head). Flexion of the head is important to facilitate engagement of the head in the maternal pelvis. When the fetal chin is optimally flexed onto the chest, the suboccipitobregmatic diameter (9.5 cm) presents at the pelvic inlet ( Fig. 12-5 ). This is the smallest possible presenting diameter in the cephalic presentation. As the head deflexes (extends), the diameter presenting to the pelvic inlet progressively increases even before the malpresentations of brow and face are encountered (see Fig. 12-5 ) and may contribute to failure to progress in labor. The architecture of the pelvic floor along with increased uterine activity may correct deflexion in the early stages of labor. FIG 12-5 Presenting diameters of the average term fetal skull. Position of the fetus refers to the relationship of the fetal presenting part to the maternal pelvis, and it can be assessed most accurately on vaginal examination. For cephalic presentations, the fetal occiput is the reference: if the occiput is directly anterior, the position is occiput anterior (OA); if the occiput is turned toward the mother’s right side, the position is right occiput anterior (ROA). In the breech presentation, the sacrum is the reference (right sacrum anterior). The various positions of a cephalic presentation are illustrated in Figure 12-6 . In a vertex presentation, position can be determined by palpation of the fetal sutures: the sagittal suture is the easiest to palpate, but palpation of the distinctive lambdoid sutures should identify the position of the fetal occiput; the frontal suture can also be used to determine the position of the front of the vertex. FIG 12-6 Fetal presentations and positions in labor. LOA, left occiput anterior; LOP, left occiput posterior; LOT, left occiput transverse; ROA, right occiput anterior; ROT, right occiput transverse; ROP, right occiput posterior. (Modified from Norwitz ER, Robinson J, Repke JT. The initiation and management of labor. In Seifer DB, Samuels P, Kniss DA, eds. The Physiologic Basis of Gynecology and Obstetrics. Philadelphia: Lippincott, Williams & Wilkins; 2001.) Most commonly, the fetal head enters the pelvis in a transverse position and then, as a normal part of labor, it rotates to an OA position. Most fetuses deliver in the OA, left occiput anterior (LOA), or ROA position. Malposition refers to any position in labor that is not in the above three categories. In the past, fewer than 10% of presentations were occiput posterior (OP) at delivery. However, epidural analgesia may be an independent risk factor for persistent OP presentation in labor. In an observational cohort study, OP presentation was observed in 12.9% of women with epidurals compared with 3.3% of controls ( P = .002). In a Cochrane meta-analysis of four randomized controlled trials (RCTs), malposition was 40% more likely for women with an epidural compared with controls; however, this difference was not statistically significant, and more RCTs are needed (odds ratio [OR] 1.40; 95% confidence interval [CI], 0.98 to 1.99). Asynclitism occurs when the sagittal suture is not directly central relative to the maternal pelvis. If the fetal head is turned such that more parietal bone is present posteriorly, the sagittal suture is more anterior; this is referred to as posterior asynclitism. In contrast, anterior asynclitism occurs more parietal bone presents anteriorly. The occiput transverse (OT) and OP positions are less common at delivery and are more difficult to deliver. Station is a measure of descent of the bony presenting part of the fetus through the birth canal ( Fig. 12-7 ). The current standard classification (−5 to +5) is based on a quantitative measure in centimeters of the distance of the leading bony edge from the ischial spines. The midpoint (0 station) is defined as the plane of the maternal ischial spines. The ischial spines can be palpated on vaginal examination at approximately 8 o’clock and 4 o’clock. For the right-handed person, they are most easily felt on the maternal right. FIG 12-7 The relationship of the leading edge of the presenting part of the fetus to the plane of the maternal ischial spines determines the station. Station +1/+3 (old classification), or +2/+5 (new classification), is illustrated. An abnormality in any of these fetal variables may affect both the course of labor and the route of delivery. For example, OP presentation is well known to be associated with longer labor, operative vaginal delivery, and an increased risk of cesarean delivery. Maternal Pelvis (Passage) The passage consists of the bony pelvis—composed of the sacrum, ilium, ischium, and pubis—and the resistance provided by the soft tissues. The bony pelvis is divided into the false (greater) and true (lesser) pelvis by the pelvic brim, which is demarcated by the sacral promontory, the anterior ala of the sacrum, the arcuate line of the ilium, the pectineal line of the pubis, and the pubic crest culminating in the symphysis ( Fig. 12-8 ). Measurements of the various parameters of the bony female pelvis have been made with great precision, directly in cadavers and using radiographic imaging in living women. Such measurements have divided the true pelvis into a series of planes that must be negotiated by the fetus during passage through the birth canal, which can be broadly termed the pelvic inlet, midpelvis, and pelvic outlet. Pelvimetry performed with radiographic computed tomography (CT) or magnetic resonance imaging (MRI) has been used to determine average and critical limit values for the various parameters of the bony pelvis ( Table 12-1 ). Critical limit values are measurements that may be associated with a significant probability of CPD depending upon fetal size and gestational age. However, subsequent studies were unable to demonstrate threshold pelvic or fetal cutoff values with sufficient sensitivity or specificity to predict CPD and the subsequent need for cesarean delivery prior to the onset of labor. In current obstetric practice, radiographic CT and MRI pelvimetry are rarely used given the lack of evidence of benefit and some data that show possible harm (increased incidence of cesarean delivery); instead, a clinical trial of the pelvis (labor) is used. The remaining indications for radiography, CT pelvimetry, or MRI are evaluation for vaginal breech delivery or evaluation of a woman who has suffered a significant pelvic fracture. FIG 12-8 Superior (A) and anterior (B) view of the female pelvis. (From Repke JT. Intrapartum Obstetrics. New York: Churchill Livingstone; 1996;68.) TABLE 12-1 AVERAGE AND CRITICAL LIMIT VALUES FOR PELVIC MEASUREMENTS BY X-RAY PELVIMETRY DIAMETER AVERAGE VALUE CRITICAL LIMIT * Pelvic Inlet Anteroposterior (cm) 12.5 10.0 Transverse (cm) 13.0 12.0 Sum (cm) 25.5 22.0 Area (cm 2 ) 145.0 123.0 Pelvic Midcavity Anteroposterior (cm) 11.5 10.0 Transverse (cm) 10.5 9.5 Sum (cm) 22.0 19.5 Area (cm 2 ) 125.0 106.0   Modified from O’Brien WF, Cefalo RC. Labor and delivery. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics: Normal and Problem Pregnancies, ed 3. New York: Churchill Livingstone; 1996;377. * The critical limit values cited imply a high likelihood of cephalopelvic disproportion. Clinical pelvimetry is currently the only method of assessing the shape and dimensions of the bony pelvis in labor. A useful protocol for clinical pelvimetry is detailed in Figure 12-9 and involves assessment of the pelvic inlet, midpelvis, and pelvic outlet. Reported average and critical-limit pelvic diameters may be used as a historical reference during the clinical examination to determine pelvic shape and assess risk for CPD. The inlet of the true pelvis is largest in its transverse diameter and averages 13.5 cm. The diagonal conjugate, the distance from the sacral promontory to the inferior margin of the symphysis pubis as assessed on vaginal examination, is a clinical representation of the anteroposterior (AP) diameter of the pelvic inlet. The true conjugate, or obstetric conjugate, of the pelvic inlet is the distance from the sacral promontory to the superior aspect of the symphysis pubis. The obstetric conjugate has an average value of 11 cm and is the smallest diameter of the inlet. It is considered to be contracted if it measures less than 10 cm. The obstetric conjugate cannot be measured clinically but can be estimated by subtracting 1.5 to 2.0 cm from the diagonal conjugate, which has an average distance of 12.5 cm. FIG 12-9 A protocol for clinical pelvimetry. The limiting factor in the midpelvis is the transverse interspinous diameter (the measurement between the ischial spines), which is usually the smallest diameter of the pelvis but should be greater than 10 cm. The pelvic outlet is rarely of clinical significance, however. The average pubic angle is greater than 90 degrees and will typically accommodate two fingerbreadths. The AP diameter from the coccyx to the symphysis pubis is approximately 13 cm in most cases, and the transverse diameter between the ischial tuberosities is approximately 8 cm and will typically accommodate four knuckles (see Fig. 12-9 ). The shape of the female bony pelvis can be classified into four broad categories: gynecoid, anthropoid, android, and platypelloid ( Fig. 12-10 ). This classification is based on the radiographic studies of Caldwell and Moloy and separates those with more favorable characteristics (gynecoid, anthropoid) from those less favorable for vaginal delivery (android, platypelloid). In reality, however, many women fall into intermediate classes, and the distinctions become arbitrary. The gynecoid pelvis is the classic female shape. The anthropoid pelvis—with its exaggerated oval shape of the inlet, largest AP diameter, and limited anterior capacity—is more often associated with delivery in the OP position. The android pelvis is male in pattern and theoretically has an increased risk of CPD, and the broad and flat platypelloid pelvis theoretically predisposes to a transverse arrest. Although the assessment of fetal size, along with pelvic shape and capacity, is still of clinical utility, it is a very inexact science. An adequate trial of labor is the only definitive method to determine whether a fetus will be able to safely negotiate through the pelvis. FIG 12-10 Characteristics of the four types of female bony pelvis. (Modified from Callahan TL, Caughey AB, Heffner LJ, eds. Blueprints in Obstetrics and Gynecology. Malden, MA: Blackwell Science; 1998;45.) Pelvic soft tissues may provide resistance in both the first and second stages of labor. In the first stage, resistance is offered primarily by the cervix, whereas in the second stage, it is offered by the muscles of the pelvic floor. In the second stage of labor, the resistance of the pelvic musculature is believed to play an important role in the rotation and movement of the presenting part through the pelvis. Cardinal Movements in Labor The cardinal movements refer to changes in the position of the fetal head during its passage through the birth canal. Because of the asymmetry of the shape of both the fetal head and the maternal bony pelvis, such rotations are required for the fetus to successfully negotiate the birth canal. Although labor and birth comprise a continuous process, seven discrete cardinal movements are described: (1) engagement, (2) descent, (3) flexion, (4) internal rotation, (5) extension, (6) external rotation or restitution, and (7) expulsion ( Fig. 12-11 ). FIG 12-11 Cardinal movements of labor. Engagement Engagement refers to passage of the widest diameter of the presenting part to a level below the plane of the pelvic inlet ( Fig. 12-12 ). In the cephalic presentation with a well-flexed head, the largest transverse diameter of the fetal head is the biparietal diameter (9.5 cm). In the breech, the widest diameter is the bitrochanteric diameter. Clinically, engagement can be confirmed by palpation of the presenting part both abdominally and vaginally. With a cephalic presentation, engagement is achieved when the presenting part is at zero station on vaginal examination. Engagement is considered an important clinical prognostic sign because it demonstrates that, at least at the level of the pelvic inlet, the maternal bony pelvis is sufficiently large to allow descent of the fetal head. In nulliparas, engagement of the fetal head usually occurs by 36 weeks’ gestation; however, in multiparas engagement can occur later in gestation or even during the course of labor. FIG 12-12 Engagement of the fetal head. Descent Descent refers to the downward passage of the presenting part through the pelvis. Descent of the fetus is not continuous; the greatest rates of descent occur in the late active phase and during the second stage of labor. Flexion Flexion of the fetal head occurs passively as the head descends owing to the shape of the bony pelvis and the resistance offered by the soft tissues of the pelvic floor. Although flexion of the fetal head onto the chest is present to some degree in most fetuses before labor, complete flexion usually occurs only during the course of labor. The result of complete flexion is to present the smallest diameter of the fetal head (the suboccipitobregmatic diameter) for optimal passage through the pelvis. Internal Rotation Internal rotation refers to rotation of the presenting part from its original position as it enters the pelvic inlet (usually OT) to the AP position as it passes through the pelvis. As with flexion, internal rotation is a passive movement that results from the shape of the pelvis and the pelvic floor musculature. The pelvic floor musculature, including the coccygeus and ileococcygeus muscles, forms a V -shaped “hammock” that diverges anteriorly. As the head descends, the occiput of the fetus rotates toward the symphysis pubis—or, less commonly, toward the hollow of the sacrum—thereby allowing the widest portion of the fetus to negotiate the pelvis at its widest dimension. Owing to the angle of inclination between the maternal lumbar spine and pelvic inlet, the fetal head engages in an asynclitic fashion (i.e., with one parietal eminence lower than the other). With uterine contractions, the leading parietal eminence descends and is first to engage the pelvic floor. As the uterus relaxes, the pelvic floor musculature causes the fetal head to rotate until it is no longer asynclitic. Extension Extension occurs once the fetus has descended to the level of the introitus. This descent brings the base of the occiput into contact with the inferior margin at the symphysis pubis. At this point, the birth canal curves upward. The fetal head is delivered by extension and rotates around the symphysis pubis. The forces responsible for this motion are the downward force exerted on the fetus by the uterine contractions along with the upward forces exerted by the muscles of the pelvic floor. External Rotation External rotation, also known as restitution, refers to the return of the fetal head to the correct anatomic position in relation to the fetal torso. This can occur to either side depending on the orientation of the fetus; this is again a passive movement that results from a release of the forces exerted on the fetal head by the maternal bony pelvis and its musculature and mediated by the basal tone of the fetal musculature. Expulsion Expulsion refers to delivery of the rest of the fetus. After delivery of the head and external rotation, further descent brings the anterior shoulder to the level of the symphysis pubis. The anterior shoulder is delivered in much the same manner as the head, with rotation of the shoulder under the symphysis pubis . After the shoulder, the rest of the body is usually delivered without difficulty. Normal Progress of Labor Progress of labor is measured with multiple variables. With the onset of regular contractions, the fetus descends in the pelvis as the cervix both effaces and dilates. With each vaginal examination to judge labor progress, the clinician must assess not only cervical effacement and dilation but fetal station and position. This assessment depends on skilled digital palpation of the maternal cervix and the presenting part. As the cervix dilates in labor, it thins and shortens—or becomes more effaced —over time. Cervical effacement refers to the length of the remaining cervix and can be reported in length or as a percentage. If percentage is used, 0% effacement at term refers to at least a 2 cm long or a very thick cervix, and 100% effacement refers to no length remaining or a very thin cervix. Most clinicians use percentages to follow cervical effacement during labor. Generally, 80% or greater effacement is observed in women who are in active labor. Dilation, perhaps the easiest assessment to master, ranges from closed (no dilation) to complete (10 cm dilated). For most women, a cervical dilation that accommodates a single index finger is equal to 1 cm, and two index fingers’ dilation is equal to 3 cm. If no cervix can be palpated around the presenting part, the cervix is 10 cm or completely dilated. The assessment of station, discussed earlier, is important for documentation of progress, but it is also critical when determining if an operative vaginal delivery is feasible. Fetal head position should be regularly determined once the woman is in active labor; ideally, this should occur before significant caput has developed, which obscures the sutures. Like station, knowledge of the fetal position is critical before performing an operative vaginal delivery (see Chapter 14 ). Labor occurs in three stages: the first stage is from labor onset until full dilation of the cervix; the second stage is from full cervical dilation until delivery of the baby; and the third stage begins with delivery of the baby and ends with delivery of the placenta. The first stage of labor is divided into two phases: the first is the latent phase, and the second is the active phase . The latent phase begins with the onset of labor and is characterized by regular, painful uterine contractions and a slow rate of cervical change. When the rate of cervical dilation is accelerated, latent labor ends and active labor begins. Labor onset is a retrospective diagnosis that is difficult to identify objectively. It is defined by the initiation of regular painful contractions of sufficient duration and intensity to result in cervical dilation or effacement. Women are frequently at home during this time; therefore the identification of labor onset depends on patient memory and the timing of contractions in relation to the cervical examination. The active phase of labor is defined as the period in which the greatest rate of cervical dilation occurs. Identification of the point at which labor transitions from the latent to the active phase will depend upon the frequency of cervical examinations and retrospective examination of labor progress. Historically, based upon Friedman’s seminal data on cervical dilation and labor progress from the 1950s and 1960s, active labor required 80% or more effacement and 4 cm or greater dilation of the cervix. He analyzed labor progress in 500 nulliparous and multiparous women and reported normative data that have been used for more than half a century to define our expectations of normal and abnormal labor. Friedman revolutionized our understanding of labor because he was able to plot static observations of cervical dilation against time and successfully translate the dynamic process of labor into a sigmoid-shaped curve ( Fig. 12-13 ). Friedman’s data popularized the use of the labor graph, which first depicted only cervical dilation and was then later modified to include fetal descent. Four-centimeter cervical dilation marks the transition from the latent to the active phase because it corresponds to the flexion point on the averaged labor curve generated from a review of 500 individual labor curves in the original Friedman dataset. Rates of 1.5 and 1.2 cm dilation per hour in the active phase for multiparous and nulliparous women, respectively, represent the 5th percentile of normal. These data have led to the general concept that in active labor, a rate of dilation of at least 1 cm per hour should occur. FIG 12-13 A, Modern labor graph. Characteristics of the average cervical dilation curve for nulliparous labor. B, Zhang labor partogram. The 95th percentiles of cumulative duration of labor from admission among singleton term nulliparous women with spontaneous onset of labor. Accel., acceleration; Decel., deceleration; Max., maximum; Sec., seconds. ( A, Modified from Friedman EA. Labor: Clinical Evaluation and Management, ed 2. Norwalk, CT: Appleton-Century-Crofts; 1978. B , From Zhang J, Landy H, Branch D, et al; the Consortium on Safe Labor. Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol. 2010;1116:1281.) More recent analysis of contemporary labor from several studies challenges our understanding of the cervical dilation at which active labor occurs and suggests that the transition from the latent phase to the active phase of labor is a more gradual process. An analysis of labor curves for 1699 multiparous and nulliparous women who presented in spontaneous labor at term and underwent a vaginal delivery determined that only half of the women with a cervical dilation of 4 cm were in the active phase. By 5 cm of cervical dilation, 75% of the women were in the active phase, and by 6 cm cervical dilation, 89% of the women were in the active phase. Zhang and colleagues reviewed data from the National Collaborative Perinatal Project, a historic cohort of 26,838 term parturients in spontaneous labor from 1959 through 1966. This study used a repeated measures analysis to construct labor curves for parturients whose intrapartum management was similar to those studied by Friedman in the 1950s. The cesarean delivery rate was 5.6%, and only 20% of nulliparas and 12% of multiparas received oxytocin for labor augmentation. This study determined that labor progress in nulliparous women who ultimately had a vaginal delivery is in fact slower than previously reported until 6 cm of cervical dilation. Specifically, most nulliparous women were not in active labor until approximately 5 to 6 cm of cervical dilation, and the slope of labor progress did not increase until after 6 cm. These findings were confirmed in an analysis of contemporary data collected prospectively by the Consortium on Safe Labor, which enrolled and followed 62,415 singleton term parturients who presented in spontaneous labor at 19 institutions from 2002 through 2007. This dataset included a greater percentage of women with oxytocin augmentation (45% to 47%) and epidural analgesia (71% to 84%) compared with those studied by Friedman in the 1950s. Zhang and colleagues reported the median and 95th percentile of time to progress from one centimeter to the next and confirmed that labor may take more than 6 hours to progress from 4 to 5 cm and more than 3 hours to progress from 5 to 6 cm regardless of parity ( Table 12-2 ). Multiparas had a faster rate of cervical dilation compared with nulliparas only after 6 cm of cervical dilation had been reached. These data suggest that it would be more appropriate to utilize a threshold of 6 cm cervical dilation to define active phase labor onset and that the rate of cervical dilation for nulliparas at the 95th percentile of normal may be greater than the 1 cm per hour previously expected. These are important findings that suggest clinicians using the Friedman dataset to determine the threshold for active labor may be diagnosing active phase arrest prematurely, which could result in unnecessary cesarean deliveries (see Chapter 13 ). TABLE 12-2 MEDIAN DURATION OF TIME ELAPSED IN HOURS FOR EACH CENTIMETER OF CHANGE IN CERVICAL DILATION IN SPONTANEOUS LABOR STRATIFIED BY PARITY CERVICAL DILATION (cm) PARITY 0 * PARITY 1 PARITY ≥2 3-4 1.8 (8.1) – – 4-5 1.3 (6.4) 1.4 ( 7.3) 1.4 (7.0) 5-6 0.8 (3.2) 0.8 (3.4) 0.8 (3.4) 6-7 0.6 (2.2) 0.5 (1.9) 0.5 (1.8) 7-8 0.5 (1.6) 0.4 (1.3) 0.4 (1.2) 8-9 0.5 (1.2) 0.3 (1.0) 0.3 (0.9) 9-10 0.5 (1.8) 0.3 (0.9) 0.3 (0.8)

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How your twins’ fetal positions affect labor and delivery

Twin fetal presentation – also known as the position of your babies in the womb – dictates whether you'll have a vaginal or c-section birth. Toward the end of pregnancy, most twins will move in the head-down position (vertex), but there's a risk that the second twin will change position after the first twin is born. While there are options to change the second twin's position, this can increase the risk of c-section and other health issues. Learn about the six possible twin fetal presentations: vertex-vertex, vertex-breech, breech-breech, vertex-transverse, breech-transverse, and transverse-transverse – and how they'll impact your delivery and risks for complications.

What is fetal presentation and what does it mean for your twins?

As your due date approaches, you might be wondering how your twins are currently positioned in the womb, also known as the fetal presentation, and what that means for your delivery. Throughout your pregnancy, your twin babies will move in the uterus, but sometime during the third trimester – usually between 32 and 36 weeks – their fetal presentation changes as they prepare to go down the birth canal.

The good news is that at most twin births, both babies are head-down (vertex), which means you can have a vaginal delivery. In fact, nearly 40 percent of twins are delivered vaginally.

But if one baby has feet or bottom first (breech) or is sideways (transverse), your doctor might deliver the lower twin vaginally and then try to rotate the other twin so that they face head-down (also called external cephalic version or internal podalic version) and can be delivered vaginally. But if that doesn't work, there's still a chance that your doctor will be able to deliver the second twin feet first vaginally via breech extraction (delivering the breech baby feet or butt first through the vagina).

That said, a breech extraction depends on a variety of factors – including how experienced your doctor is in the procedure and how much the second twin weighs. Studies show that the higher rate of vaginal births among nonvertex second twins is associated with labor induction and more experienced doctors, suggesting that proper delivery planning may increase your chances of a vaginal birth .

That said, you shouldn't totally rule out a Cesarean delivery with twins . If the first twin is breech or neither of the twins are head-down, then you'll most likely have a Cesarean delivery.

Research also shows that twin babies who are born at less than 34 weeks and have moms with multiple children are associated with intrapartum presentation change (when the fetal presentation of the second twin changes from head-down to feet first after the delivery of the first twin) of the second twin. Women who have intrapartum presentation change are more likely to undergo a Cesarean delivery for their second twin.

Here's a breakdown of the different fetal presentations for twin births and how they will affect your delivery.

Head down, head down (vertex, vertex)

This fetal presentation is the most promising for a vaginal delivery because both twins are head-down. Twins can change positions, but if they're head-down at 28 weeks, they're likely to stay that way.

When delivering twins vaginally, there is a risk that the second twin will change position after the delivery of the first. Research shows that second twins change positions in 20 percent of planned vaginal deliveries. If this happens, your doctor may try to rotate the second twin so it faces head-down or consider a breech extraction. But if neither of these work or are an option, then a Cesarean delivery is likely.

In vertex-vertex pairs, the rate of Cesarean delivery for the second twin after a vaginal delivery of the first one is 16.9 percent.

Like all vaginal deliveries, there's also a chance you'll have an assisted birth, where forceps or a vacuum are needed to help deliver your twins.

Head down, bottom down (vertex, breech)

When the first twin's (the lower one) head is down, but the second twin isn't, your doctor may attempt a vaginal delivery by changing the baby's position or doing breech extraction, which isn't possible if the second twin weighs much more than the first twin.

The rates of emergency C-section deliveries for the second twin after a vaginal delivery of the first twin are higher in second twins who have a very low birth weight. Small babies may not tolerate labor as well.

Head down, sideways (vertex, transverse)

If one twin is lying sideways or diagonally (oblique), there's a chance the baby may shift position as your labor progresses, or your doctor may try to turn the baby head-down via external cephalic version or internal podalic version (changing position in the uterus), which means you may be able to deliver both vaginally.

Bottom down, bottom down (breech, breech)

When both twins are breech, a planned C-section is recommended because your doctor isn't able to turn the fetuses. Studies also show that there are fewer negative neonatal outcomes for planned C-sections than planned vaginal births in breech babies.

As with any C-section, the risks for a planned one with twins include infection, loss of blood, blood clots, injury to the bowel or bladder, a weak uterine wall, placenta abnormalities in future pregnancies and fetal injury.

Bottom down, sideways (breech, transverse)

When the twin lowest in your uterus is breech or transverse (which happens in 25 percent of cases), you'll need to have a c-section.

Sideways, sideways (transverse, transverse)

This fetal presentation is rare with less than 1 percent of cases. If both babies are lying horizontally, you'll almost definitely have a C-section.

Learn more:

• Twin fetal development month by month
• Your likelihood of having twins or more
• When and how to find out if you’re carrying twins or more

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BabyCenter's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organizations, professional groups of doctors and other experts, and published studies in peer-reviewed journals. We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies .

Cleveland Clinic. Fetal Positions for Birth: https://my.clevelandclinic.org/health/articles/9677-fetal-positions-for-birth Opens a new window [Accessed July 2021]

Mayo Clinic. Fetal Presentation Before Birth: https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/multimedia/fetal-positions/sls-20076615?s=7 Opens a new window [Accessed July 2021]

NHS. Giving Birth to Twins or More: https://pubmed.ncbi.nlm.nih.gov/29016498/ Opens a new window [Accessed July 2021]

Science Direct. Breech Extraction: https://www.sciencedirect.com/topics/medicine-and-dentistry/breech-extraction Opens a new window [Accessed July 2021]

Obstetrics & Gynecology. Clinical Factors Associated With Presentation Change of the Second Twin After Vaginal Delivery of the First Twin https://pubmed.ncbi.nlm.nih.gov/29016498/ Opens a new window [Accessed July 2021]

American Journal of Obstetrics and Gynecology. Fetal presentation and successful twin vaginal delivery: https://www.ajog.org/article/S0002-9378(04)00482-X/fulltext [Accessed July 2021]

The Journal of Maternal-Fetal & Neonatal Medicine. Changes in fetal presentation in twin pregnancies https://www.tandfonline.com/doi/abs/10.1080/14767050400028592 Opens a new window [Accessed July 2021]

Reviews in Obstetrics & Gynecology. An Evidence-Based Approach to Determining Route of Delivery for Twin Gestations https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3252881/ Opens a new window [Accessed July 2021]

Nature. Neonatal mortality and morbidity in vertex–vertex second twins according to mode of delivery and birth weight: https://www.nature.com/articles/7211408 Opens a new window [Accessed July 2021]

Cochrane. Planned cesarean for a twin pregnancy: https://www.cochrane.org/CD006553/PREG_planned-caesarean-section-twin-pregnancy Opens a new window [Accessed July 2021]

Kids Health. What Is the Apgar Score?: https://www.kidshealth.org/Nemours/en/parents/apgar0.html Opens a new window [Accessed July 2021]

American Journal of Obstetrics & Gynecology. Neonatal mortality in second twin according to cause of death, gestational age, and mode of delivery https://pubmed.ncbi.nlm.nih.gov/15467540/ Opens a new window [Accessed July 2021]

Lancet. Planned cesarean section versus planned vaginal birth for breech presentation at term: a randomised multicentre trial. Term Breech Trial Collaborative Group https://pubmed.ncbi.nlm.nih.gov/11052579/ Opens a new window [Accessed July 2021]

Cleveland Clinic. Cesarean Birth (C-Section): https://my.clevelandclinic.org/health/treatments/7246-cesarean-birth-c-section Opens a new window [Accessed July 2021]

St. Jude Medical Staff. Delivery of Twin Gestation: http://www.sjmedstaff.org/documents/Delivery-of-twins.pdf Opens a new window [Accessed July 2021]

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The ABCs of Cephalic Presentation: A Comprehensive Guide for Moms-to-Be

Updated on 24 November 2023

As expectant mothers eagerly anticipate the arrival of their little ones, understanding the intricacies of pregnancy becomes crucial. One term that frequently arises in discussions about childbirth is "cephalic presentation." In this article, we will understand its meaning, types, benefits associated with it, the likelihood of normal delivery and address common concerns expectant mothers might have.

What is the meaning of cephalic presentation in pregnancy?

Cephalic presentation means the baby's head is positioned down towards the birth canal, which is the ideal fetal position for childbirth. This position is considered optimal for a smoother and safer delivery. In medical terms, a baby in cephalic presentation is said to be in a "vertex" position.

The majority of babies naturally assume a cephalic presentation before birth. Other presentations, such as breech presentation (where the baby's buttocks or feet are positioned to enter the birth canal first) or transverse presentation (where the baby is lying sideways), may complicate the delivery process and may require medical intervention.

Cephalic presentation types

There are different types of cephalic presentation, each influencing the birthing process. The primary types include:

1. Vertex Presentation

The most common type where the baby's head is down, facing the mother's spine.

2. Brow Presentation

The baby's head is slightly extended, and the forehead presents first.

3. Face Presentation

The baby is positioned headfirst, but the face is the presenting part instead of the crown of the head.

Understanding these variations is essential for expectant mothers and healthcare providers to navigate potential challenges during labor.

You may also like: How to Get Baby in Right Position for Birth?

What are the benefits of cephalic presentation?

In order to understand whether cephalic presentation is good or bad, let’s take a look at its key advantages:

1. Easier Engagement

This presentation facilitates the baby's engagement in the pelvis, aiding in a smoother descent during labor.

2. Reduced Risk of Complications

Babies in head-first position typically experience fewer complications during delivery compared to other presentations.

3. Faster Labor Progression

This position is associated with quicker labor progression, leading to a potentially shorter and less stressful birthing process.

4. Lower Cesarean Section Rates

The chances of a cesarean section are significantly reduced when the baby is in cephalic presentation in pregnancy.

5. Optimal Fetal Oxygenation

The head-first position allows for optimal oxygenation of the baby as the head can easily pass through the birth canal, promoting a healthy start to life.

What are the chances of normal delivery in cephalic presentation?

The chances of a normal delivery are significantly higher when the baby is in cephalic or head-first presentation. Vaginal births are the natural outcome when the baby's head leads the way, aligning with the natural mechanics of childbirth.

While this presentation increases the chances of a normal delivery, it's important to note that individual factors, such as the mother's pelvic shape, the size of the baby, and the progress of labor, can also influence the delivery process. Sometimes complications may arise during labor and medical interventions or a cesarean section may be necessary.

You may also like: Normal Delivery Tips: An Expecting Mother's Guide to a Smooth Childbirth Experience

How to achieve cephalic presentation in pregnancy?

While fetal positioning is largely influenced by genetic and environmental factors, there are strategies to encourage head-first fetal position:

1. Regular Exercise

Engaging in exercises such as pelvic tilts and knee-chest exercises may help promote optimal fetal positioning.

2. Correct Posture

Maintaining good posture, particularly during the third trimester , can influence fetal positioning.

3. Hands and Knees Position

Spend some time on your hands and knees. This position may help the baby settle into the pelvis with the head down.

4. Forward-leaning Inversion

Under the guidance of a qualified professional, some women try forward-leaning inversions to encourage the baby to move into a head-down position. This involves positioning the body with the hips higher than the head.

5. Prenatal Yoga

Prenatal yoga focuses on strengthening the pelvic floor and promoting flexibility, potentially aiding in cephalic presentation.

6. Professional Guidance

Seeking guidance from a healthcare provider or a certified doula can provide personalized advice tailored to individual needs.

1. Cephalic presentation is good or bad?

Cephalic position is generally considered good as it aligns with the natural process of childbirth. It reduces the likelihood of complications and increases the chances of a successful vaginal delivery . However, it's essential to note that the overall health of both the mother and baby determines its appropriateness.

2. How to increase the chances of normal delivery in cephalic presentation?

Increasing the chances of normal delivery in cephalic presentation involves adopting healthy practices during pregnancy, such as maintaining good posture, engaging in appropriate exercises, and seeking professional guidance. However, individual circumstances vary, and consultation with a healthcare provider is paramount.

Final Thoughts

Navigating the journey of pregnancy involves understanding various aspects, and cephalic presentation plays a crucial role in determining the birthing experience. The benefits of a head-first position, coupled with strategies to encourage it, empower expectant mothers to actively participate in promoting optimal fetal positioning. As always, consulting with healthcare professionals ensures personalized care and guidance, fostering a positive and informed approach towards childbirth.

1. Makajeva J, Ashraf M. Delivery, Face and Brow Presentation. (2023). In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing

2. Boos R, Hendrik HJ, Schmidt W. (1987). Das fetale Lageverhalten in der zweiten Schwangerschaftshälfte bei Geburten aus Beckenendlage und Schädellage [Behavior of fetal position in the 2d half of pregnancy in labor with breech and vertex presentations]. Geburtshilfe Frauenheilkd

Anupama Chadha

Anupama Chadha, born and raised in Delhi is a content writer who has written extensively for industries such as HR, Healthcare, Finance, Retail and Tech.

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