variable presentation in ultrasound

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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.

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Fetal biophysical profile

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Citation, DOI, disclosures and article data

At the time the article was created Yuranga Weerakkody had no recorded disclosures.

At the time the article was last revised Henry Knipe had the following disclosures:

• Integral Diagnostics, Shareholder (ongoing)
• Micro-X Ltd, Shareholder (ongoing)

These were assessed during peer review and were determined to not be relevant to the changes that were made.

• Fetal biophysical profile (BPP)
• Fetal biophysical profile score (BPS)
• Biophysical profile score
• Biophysical profile

Fetal biophysical profile score (BPS or BPP) refers to the assessment of four discrete biophysical variables by ultrasound. It is a standard tool in antepartum fetal assessment. It is usually assessed after 28 weeks of gestation.

Radiographic features

The ultrasound variables are:

fetal breathing movements : considered abnormal if there is

absent breathing 

no breathing episode for ≥30 seconds within a 30-minute observation period

fetal tone: considered abnormal if there is 

slow extension with a return to partial flexion

absent fetal movement

fetal movement (gross body movement): considered abnormal if there is 

<2 episodes of body/limb movements within a 30-minute lapse

amniotic fluid volume : considered abnormal if the largest pocket is <2 x 2 cm

Each of these parameters is given a score of either 0 or 2 points, where an abnormal score gets 0 while a normal score gets 2.

Therefore on ultrasound assessment, a total score is given out of 8. An overall abnormal score out of 8 is often taken as 4/8 or less.

A continuous observation for at least 30 minutes is must, before defining any variable as “absent”, due to fetal sleep wake cycles 7 .

In addition to this, an additional non sonographic variable ( non-stress test ) with two extra points can also be taken into account. In which case a score is given out of 10.

Potential confounding variables

Some reports show maternal fasting resulting in reduced fetal breathing movements which can in turn affect the BPP score 5 . 

Additional work up

Umbilical arterial Doppler assessment  is usually additionally carried out to evaluate fetuses with abnormal BPP scores.

History and etymology

The score was initially proposed by F A Manning et al. in 1980 3 .

• 1. Guimarães Filho H, Araujo Júnior E, Nardozza L, Dias da Costa L, Moron A, Mattar R. Ultrasound Assessment of the Fetal Biophysical Profile: What Does an Radiologist Need to Know? Eur J Radiol. 2008;66(1):122-6. doi:10.1016/j.ejrad.2007.05.011 - Pubmed
• 2. Manning F, Morrison I, Lange I, Harman C, Chamberlain P. Fetal Biophysical Profile Scoring: Selective Use of the Nonstress Test. Am J Obstet Gynecol. 1987;156(3):709-12. doi:10.1016/0002-9378(87)90083-4 - Pubmed
• 3. Manning F, Platt L, Sipos L. Antepartum Fetal Evaluation: Development of a Fetal Biophysical Profile. Am J Obstet Gynecol. 1980;136(6):787-95. doi:10.1016/0002-9378(80)90457-3 - Pubmed
• 4. Manning F. Fetal Biophysical Profile. Obstet Gynecol Clin North Am. 1999;26(4):557-77, v. doi:10.1016/s0889-8545(05)70099-1 - Pubmed
• 5. Mirghani H, Weerasinghe D, Ezimokhai M, Smith J. The Effect of Maternal Fasting on the Fetal Biophysical Profile. Int J Gynaecol Obstet. 2003;81(1):17-21. doi:10.1016/s0020-7292(02)00398-3 - Pubmed
• 6. Sapoval J, Singh V, Carter R. Ultrasound Biophysical Profile. 2021. - Pubmed
• 7. Carol M. Rumack. Diagnostic Ultrasound. (2011) ISBN: 9780323053976 - Google Books

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• Introduction
• Definitions
• Perinatal Morbidity And Mortality
• Complications And Counseling
• Intrapartum Complications And Counseling
• Intrapartum Management
• Management Of Labor And Delivery
• Cesarean Delivery
• Perinatal Outcome

Abnormal Fetal Lie and Presentation

Introduction.

The normal process of parturition relies in part, on the physical relationships between the fetus and maternal bony outlet. In addition, fetal posture, placental and cord locations, as well as maternal soft tissues also are factors in the efficiency and safety of the birth process.

This chapter discusses how to define, diagnose, and manage the clinical impact of abnormalities of fetal lie and malpresentation. The most common clinical correlation of the abnormal fetal lies and presentations is the breech-presenting fetus.

DEFINITIONS

In describing fetopelvic relationships, the clinician should carefully adhere to standard obstetrical nomenclature. Fetal lie refers to the relationship between the long axis of the fetus with respect to the long axis of the mother. The possibilities include a longitudinal lie, a transverse lie, and, on occasion, an oblique lie. Fetal presentation is a reference to the part of the fetus that is overlying the maternal pelvic inlet.

The most common relationship between fetus and mother is the longitudinal lie, cephalic presentation. A breech fetus also is a longitudinal lie, with the fetal buttocks as the presenting part. Breech fetuses also are referred to as malpresentations because of the many problems associated with them. Fetuses that are in a transverse lie may present the fetal back (or shoulders, as in the acromial presentation), small parts (arms and legs), or the umbilical cord (as in a funic presentation) to the pelvic inlet. In an oblique lie, the fetal long axis is at an angle to the bony inlet, and no palpable fetal part generally is presenting. This lie usually is transitory and occurs during fetal conversion between other lies.

The most dependent portion of the presenting part is known as the point of direction. The occiput is the point of direction of a well-flexed fetus in cephalic presentation. The fetal position refers to the location of the point of direction with reference to the four quadrants of the maternal outlet as viewed by the examiner. Thus, position may be right or left as well as anterior or posterior.

Fetal attitude refers to the posture of a fetus during labor. Mammalian fetuses have a tendency to assume a fully flexed posture during development and during parturition. Flexion of the fetal head on the chest allows for the delivery of the head by its smallest bony diameter. A loss of this flexed posture presents a progressively larger fetal head to the bony pelvis for labor and delivery (Fig. 1). The fetal arms and legs also tend to assume a fully flexed posture. The longitudinal posture of the fetus likewise is flexed under normal circumstances.

The mechanism of labor and delivery, as well as its inherent safety and efficacy, is determined by the specifics of the fetopelvic relationship at the onset of labor. Further correlations with fetopelvic relationships are important before birth.

The relative incidence of differing fetopelvic relations varies with diagnostic and clinical approaches to care. Among longitudinal lies, about 1 in 25 fetuses are not cephalic but breech at the onset of labor. 1 Of the differing lies a fetus may assume, about 1 in 100 is transverse or oblique, also referred to as nonaxial.

As pregnancy proceeds to term, most fetuses assume a longitudinal lie with relationship with the maternal outlet. Conversely, when labor and delivery are considered to be remote from term, the proportion of fetuses in abnormal and suboptimal locations increases ( Table 1 ).

Table 1. Breech presentation by gestational age

Transverse and oblique lies also are seen with greater frequency earlier in gestation. A fetus in a transverse lie may present the shoulder or acromion as a point of reference to the examiner. As term approaches, spontaneous conversion to a longitudinal lie is the norm. As seen with breech presentation, there is a rapid decrease in nonaxial lie during the third trimester. With the comprehensive application of ultrasound in the antepartum period, discovery of a transverse or oblique lie has increased. However, nonaxial fetal lies usually are transitory.

Abnormal fetal lie frequently is seen in multifetal gestation, particularly with the second twin. A transverse lie may be encountered with large discrepancies in fetopelvic parameters, such as exist with extreme prematurity and macrosomia. This tendency is greater in women of grand parity, in whom relaxation of the abdominal and uterine musculature is cited as the predisposing factor. Distortion of the uterine cavity shape, such as that seen with leiomyomas, prior uterine surgery, or developmental anomalies (Mullerian fusion defects), coexists with both abnormalities in fetal lie and malpresentation. Placental location also may play a contributing role. Fundal and cornual implantation are seen more frequently in breech presentation. Placenta previa is a well-described concomitant in both transverse lie and breech presentation. 2

Congenital anomalies of the fetus also are seen in association with abnormalities in either presentation or lie. 3 Whether a cause (as in fitting the uterine cavity optimally) or effect (the fetus with a neuromuscular condition that prevents the normal turning mechanism), the finding of an abnormal lie or malpresentation requires a thorough search for fetal maldevelopment. Abnormalities seen include chromosomal (autosomal trisomy) and structural abnormalities (hydrocephalus), as well as syndromes of multiple effects (fetal alcohol syndrome) ( Table 2 ).

Table 2. Anomalies frequently diagnosed in breech fetuses

Congenital anomalies of major structures are seen in 3–5% of all births. The incidence in breech delivery is three times greater when controlled for gestational age. Among premature breech infants, the incidence is even greater, as it is for all fetuses born prematurely.

Prematurity is a crucial factor in the incidence as well as the clinical implications of abnormal fetal lie and malpresentation. Fetal size and shape undergo dramatic change during the second and third trimester (Fig. 2, Table 3 ).

Table 3. Head circumference: abdominal circumference ratio by gestational age

SD, standard deviations (Adapted from Campbell S, Metreweli C [eds]: Practical Abdominal Ultrasound. Chicago, Year Book Medical Publishers, 1978)

Because the fetus has a relatively larger head than body during most of the late second and early third trimester, the fetus tends to spend much of its time in breech presentation or in a nonaxial lie as it rotates back and forth between cephalic and breech presentations. The relatively large volume of amniotic fluid present facilitates these dynamics.

Breech presentation is more common at earlier gestation and therefore is seen more frequently among low-birth weight infants 4 ( Table 4 ). Breech infants are more likely to be small for gestational age regardless of their gestation at delivery.

Table 4. Incidence of breech presentation by birth weight

The small size of the premature fetus is further compromised by the specific malpresentations that occur. With less neurologic and muscular control, deflexed or even extended varieties of fetal presentations are seen. Most common are the “incomplete” types of breech presentation, such as footling breech presentations (Fig. 3, Tables 5 and 6 ). Deflexion of the fetal head, more commonly seen in preterm fetuses, results in the potential for further compromise at delivery.

Table 5. Varieties of breech presentation

Table 6. Type of breech presentation in labor by gestational age

(Adapted from Gimovsky M, Petrie RH: Breech presentation. In Evans M, Fletcher J, Dixler A et al [eds]: Fetal Diagnosis and Therapy, pp 276–295. Philadelphia, JB Lippincott, 1989.)

Thus, the problems associated with abnormal lie and malpresentation are most frequent and of greatest consequence in preterm labor and delivery. At term, similar, though usually less dramatic, consequences may be seen with fetuses who are in abnormal positions.

PERINATAL MORBIDITY AND MORTALITY

Perinatal morbidity and mortality is threefold higher in breech presentation than cephalic presentation. Much of this excessive compromise is caused by factors that are not directly preventable. According to Kaupilla, 5 64% of deaths among term breech infants resulted from congenital malformations or infection. In a different population, Todd and Steer 6 found that 23 of 34 term breech deaths among 1006 term infants were not related to complications of breech delivery but were associated with anomalies, infection, and isoimmunization.

As noted earlier, preterm and small-for-gestational age infants commonly are associated with breech labor and delivery. As for term breech infants, experience indicates that most of the adverse outcomes seen are unrelated to breech delivery. Thus, for all breech fetuses, about one third of the excessive perinatal loss falls to birth trauma and asphyxia.

COMPLICATIONS AND COUNSELING

The complications associated with abnormal fetal lie and malpresentations include both maternal and fetal. As noted earlier, prematurity and malpresentation are strongly related. Circumstances in which premature birth may occur also include maternal complications such as pregnancy-induced hypertension and medical complications (cardiovascular, neoplastic), as well as obstetric problems such as premature rupture of membranes and chorioamnionitis. The circumstances dictating delivery may further compromise the preterm fetus.

The obstetric complications for the fetus include a diverse group of misadventures. Prolapse of the umbilical cord, intrauterine infection, maldevelopment as a result of oligohydramnios, asphyxia, and birth trauma all are concerns.

Birth trauma, particularly to the head and cervical spine, is a significant risk to both term and preterm infants who present as breech presentation or in a nonaxial lie. 7 , 8 , 9 Unlike the cephalic fetus in whom hours of adaptation to the maternal bony pelvis (molding) may occur, the after-coming head of the breech fetus must descend and deliver rapidly and without significant change in shape. Therefore, small alterations in the dimensions or shape of the maternal bony pelvis or the attitude of the fetal head may have grave consequences. As discussed earlier, this process is of greater risk to the preterm infant because of the relative size of the fetal head and body. Trauma to the head is not eliminated by cesarean section; both intracranial and cervical spine trauma may result from entrapment in either the uterine or abdominal incisions. 10

The fetus in the transverse lie, regardless of gestational age, generally requires cesarean delivery. At cesarean section, delivery may be aided by converting the fetus to a longitudinal lie for the delivery after entering the abdomen. This conversion may allow for the use of a transverse incision into the uterus instead of the more morbid vertical incision.

External cephalic version (ECV) should be considered in a nonlaboring patient. When the diagnosis is first made at term, spontaneous conversion to a longitudinal lie is less common than for its breech counterpart. This results from the higher incidence of structural causes for the transverse lie.

When abnormal presentation or lie occurs in a twin gestation, management includes a greater range of options. The conversion of a backup transverse second twin, either by internal or external version at the time of delivery, is an option for the experienced clinician. When the back is down at the time of delivery, the prudent course for the delivery of a fetus in transverse lie is by cesarean section. Strong consideration should be given to the incisions at delivery in this circumstance, with a vertical uterine incision being used liberally.

When a fetus in a transverse lie is diagnosed remote from delivery, as occurs at time of ultrasound, the physician is faced with an additional dilemma. Spontaneous rupture of membranes may result in cord prolapse or compromise with the risk of fetal asphyxia. Delivery at the time of antepartum ultrasound before term may result in jeopardy because of prematurity. External version, as a correction, may be attempted as long as ultrasound excludes placenta previa and documents an appropriate amount of amniotic fluid. Experience has demonstrated some success, although in general, the use of ECV is more likely to be successful for a breech-presenting fetus.

The patient should be carefully counseled about the problem and its inherent risks. Hospitalization and observation may be considered. However, the cost–benefit ratio in this era of managed care makes prolonged hospitalization unlikely under most circumstances. I recommend twice-weekly fetal surveillance to assess for cord compromise. The patient should be warned about the signs and symptoms of preterm labor and encouraged to present to labor and delivery should these conditions arise. Under certain circumstances, home uterine activity monitoring may provide a useful adjunct.

The antepartum diagnosis of persistent breech presentation is accompanied by similar concerns. In addition, careful evaluation for fetal anomalies is warranted. A targeted ultrasound by an experienced ultrasonographer is useful to diagnosis structural fetal defects and to ascertain appropriate fetal growth. Prenatal diagnosis by maternal screening or amniocentesis may be indicated.

When premature rupture of membranes occurs, consideration of a timely delivery should ensue. Depending on gestational age, amniotic fluid volume, and cervical evaluation, a limited course of tocolysis, antibiotics, and steroid administration may be indicated. When a fetus with an abnormal lie or malpresentation presents under these circumstances, hospital care is best managed within the confines of labor and delivery, where fetal surveillance can be maintained on a continual basis. This is indicated primarily because of the risk of cord prolapse or compromise. With severe oligohydramnios, the high incidence of intrauterine infection adds measurably to the risks of maintaining the fetus in utero, and an expedited delivery is warranted routinely.

INTRAPARTUM COMPLICATIONS AND COUNSELING

As previously discussed, the new intrapartum diagnosis of a transverse lie generally results in an expedited cesarean delivery. When a transverse lie is associated with prolapse of the umbilical cord, a true obstetric emergency may arise. Pelvic examination, with relief of pressure against the umbilical cord, should be performed and parenteral tocolysis administered if contraindications are not present. Changes in maternal positioning, particularly the lateral supine position, usually are well tolerated by both patient and practitioner.

Transport to a delivery room equipped for cesarean delivery should be accomplished promptly. When setup is complete, abdominal delivery is performed. A consideration for a limited attempt at version may play a role in this clinical scenario after anesthesia has been satisfactorily obtained.

Clinically more common is the diagnosis of a breech presentation at or near term. Prenatal visits in the third trimester should include Leopold maneuvers and should frequently include ultrasound as an adjunct. Also, they should always include the consideration that malpresentation may exist. The diagnosis of this situation before the onset of labor should be the goal because this allows for a larger and safer range of options. 11

After a diagnosis is confirmed, the patient deserves as thorough an explanation as is called for by the specific situation. She likely has heard, at least peripherally, that a breech baby means a mandatory cesarean section.

Whereas there is some truth in this simple association, I strongly believe that as the patient's advocate, physicians undertake the responsibility to provide a fuller discussion. Most breech fetuses at term are not a complex problem. Most do not have congenital anomalies or other adverse obstetric problems. Their potential problem centers on the risks of asphyxia and trauma during labor and delivery.

Clearly, this group of risks, however clinicians clinically work to minimize them, are best avoided if possible. Therefore, the diagnosis of breech presentation before labor allows the patient to undergo ECV and hopefully delivery as a cephalic fetus (Fig. 4). ECV is a time-honored approach to correct a “malpresentation.” It was used in the past as soon as the diagnosis of a breech fetus was made. This led to many second-trimester and early third-trimester procedures. Given the size of the fetus and the quantity of amniotic fluid present, it is not surprising that the failure rate was high. Because most of these fetuses would have spontaneously converted to cephalic presentations at the time of labor, using ECV resulted in many unnecessary procedures 12 ( Table 7 ).

Table 7. Spontaneous conversion of breech to cephalic presentation

(Adapted from Westgren M, Edvall H, Nordstrom L et al: Spontaneous cephalic version of breech presentation in the last trimester. Br J Obstet Gynaecol 92:19, 1985)

In fact, the earlier practitioners of the 20th century used sufficient force to avoid the need for a cesarean section under these circumstances that general anesthesia was used, as well as regional anesthesia and analgesics. Unfortunately, the great forces were associated with serious trauma to the placenta and uterus. Spontaneous rupture of both the uterus and the membranes, placental abruption, and fetal isoimmunization also were seen and resulted in the abandonment of this approach.

ECV performed on a fetus at term and in the absence of maternal anesthesia or analgesia made a return to practice in the 1970s. 13 , 14 By performing ECV at term, spontaneous conversion reduced the population at need for a cesarean section for breech presentation. 12 By performing ECV at term and within the labor and delivery area, means were available for immediate cesarean delivery if a problem ensued. Several groups have demonstrated a high degree of success with ECV in the late third trimester. 15 , 16 , 17

Even under these circumstances and safeguards, ECV is not entirely risk free. Although usually of no clinical consequence, fetal bradycardia is common during the procedure. Antepartum bleeding, isoimmunization, and fetal death (acute and remote) have been described. 18 Furthermore, conversion may cause deflexion of the fetal head or result in a funic presentation, either of which might require a cesarean delivery in and of itself. 19 , 20

If ECV fails or if the patient finds it unacceptable, at least two further choices remain. The first is delivery by cesarean section. If the patient is a candidate, the second is a selective trial of labor.

Once the diagnosis of breech presentation has been confirmed and attempts at ECV have failed, both patient and physician require a heightened effort at communication to ensure that a plan of care is established that is mutually acceptable. Potential risks for the breech fetus approaching term include umbilical cord prolapse, prolapse of the fetus before complete cervical dilation is achieved, and a rapidly progressive labor, with delivery imminent on arrival or even en route to labor and delivery.

Prolapse of the umbilical cord is an unusual complication in a term fetus in the early stages of labor. Because a breech fetus presents a smaller and less complete covering to the pelvic inlet, this risk is greater for all breech fetuses in comparison with all cephalic fetuses. Among breech fetus, the less complete the flexion of the lower extremities—such as occurs in footling breech presentations—the greater the risk.

Other factors, however, play a role in mitigating or increasing this risk. The nonasphyxiated fetus generally possesses a turgid umbilical cord, coated in Wharton jelly. With normal blood flow, cord prolapse is unlikely, regardless of position. Prolapse of the cord also is decidedly more common in the second stage of labor, when maternal expulsive efforts result in expression of the uterine contents ( Table 8 ).

Table 8. External cephalic version late in pregnancy

The exception occurs when the cord is located as the most dependent fetal part at the onset of labor, as seen in funic presentations. Ultrasound examination, in conjunction with color Doppler scan, can help to locate the exact position of the umbilical cord and should be performed at the time of ECV.

Prolapse of the fetus before achieving full cervical dilation, particularly in a rapidly progressive labor, is another concern. The fetus most likely to experience adverse consequences from this complication has a low birth weight and usually is preterm. 21 The breech fetus that is incomplete in flexion (the single- and double-footling varieties) has a greater tendency to prolapse under this premature descent. Unfortunately, this group is disproportionately represented in fetuses delivering preterm. The most common breech fetuses, frank and complete presentations, comprise most breech fetuses at term. Their risk of cord prolapse, or body prolapse before second stage, is only marginally greater than their cephalic counterparts. Thus, the patient and physician confronted with a frank or complete breech presentation at term and after a failed attempt at ECV should be reassured that although these risks exist, their occurrence is rare, in the order of 1 to 3 per 1000. 22

What about the woman with extremely rapid labor, or the patient who resides at a great distance from the hospital? Delivery of a breech fetus requires an experienced clinician to ensure the maximum safety of both infant and mother. Serious consideration should be given to induction of labor at term, after fetal lung maturation is assured. Cervical ripening and induction of labor may be conducted in the same manner as for a cephalic fetus. By scheduling the delivery of a breech fetus, either by cesarean section or by induction, the proper resources, both personnel and equipment, can be assured. 23 , 24

If a cesarean section is chosen, appropriate arrangements can be made, as delineated earlier in reference to a scheduled induction of labor. Cesarean section before the onset of labor avoids the additional risks of both cord prolapse and body prolapse before complete dilation and is associated with a lessened risk of anesthesia for the parturient. 25

INTRAPARTUM MANAGEMENT

Cesarean delivery has been liberally used to decrease perinatal mortality and morbidity for the breech fetus. The potential to avoid birth trauma and asphyxia led to its application to a greater extent even in the early part of the 20th century, when the safety of cesarean delivery was in greater question. As its use increased, the perinatal mortality associated with a live, nonanomalous fetus at term dropped dramatically 26 (Fig. 5).

Wright, in 1959, 27 called for the exclusive use of cesarean delivery for breech fetuses. In this and earlier eras, prematurity, low birth weight, or congenital anomalies went untreated or undertreated, and so the only group of breech fetuses that had a chance for survival were those infants born of normal weight at term. With the avoidance of intrapartum asphyxia or birth trauma sustained during delivery, the outcome could be improved. Indeed, a great difference in outcome was attributed by some to the risks of labor and delivery 28 ( Table 9 ).

Table 9. Outcome of breech infants weighing more than 2500 g, 1973–1980

(Adapted from Weingold AB: The Management of Breech Presentation. In Iffy L, Charles C [eds]: Operative Perinatology, pp 357–553. New York, Macmillan, 1984)

Although the liberal use of cesarean delivery is indicated for breech fetuses, there is concern about whether its routine use is warranted. In a study by Green and coworkers, 29 the rate of cesarean delivery for breech increased from 22% to 94% on the same medical service over a 15-year interval. Despite this extensive application of cesarean delivery, the perinatal outcome, as measured by evidence of asphyxia, trauma, or intrapartum death, was unchanged ( Table 10 ).

Table 10. Outcome of breech presenting fetuses at term by method of delivery

Cesarean delivery increases maternal morbidity and mortality, albeit to a lesser extent than in the past. The relative risks and benefits to both mother and infant should be presented by the physician to the patient ( Table 11 ). The cost, both economic and psychological, of cesarean delivery also has been debated. In past eras, a greater dollar cost was associated with abdominal delivery. With shorter stays and improved approaches to cesarean delivery, the difference has narrowed.

Table 11. Perinatal and maternal morbidity associated with breech labor and delivery

Another approach is the selective use of a trial of labor. By identifying which breech fetuses and mothers have the greatest predictable risk, cesarean delivery can be used for the group likely to have the greatest gain. By avoiding cesarean delivery in the low-risk pairings, use of cesarean delivery can be minimized, with subsequent savings to the health system of limited resources.

Many authors realize the potential benefits of such an approach. 30 , 31 , 32 At a 4% incidence and at 4 million births a year, some 160,000 pregnancies are complicated by a breech-presenting fetus at term on an annual basis. At a rate of cesarean delivery of about 90%, this results in 144,000 procedures, almost one-fifth that of cesarean delivery. By selecting a low-risk group for a trial of labor, the overall use of cesarean delivery for this indication might be reduced to 50%, saving more than 60,000 major surgeries a year, or 8% of the total cesarean deliveries performed.

This savings would be moot if there were a corresponding increase in perinatal morbidity and mortality associated with this practice shift. The available data on selective trials of labor support such an approach and suggest that the additional fetal risk is minimal and justified by the reduction in maternal morbidity and mortality.

Some of the factors for consideration in determining the risks for an individual patient already have been mentioned. Given the size and shape of the low birth weight breech fetus, most authors agree that fetuses who are breech and require delivery between 1000 and 2000 g are best served by cesarean delivery. The group of preterm fetuses weighing less than 1000 g and in need of delivery require individual assessment. The trauma to be avoided at vaginal delivery may occur at cesarean delivery. The need for vertical uterine incisions, which may require extension into the fundus, makes breech extraction difficult. This is particularly true in the presence of ruptured membranes. Entrapment of the after-coming head is of particular concern in this weight group. As outlined earlier, the head–abdomen ratio and the incidence if “incomplete” types of breech fetuses are predisposing factors. Entrapment occurs at both cesarean delivery and vaginal deliveries with these low birth weight infants. Delivery “en caul” may mitigate against head entrapment at cesarean delivery or vaginal delivery after the delivery of the small fetus.

At the other extreme, the macrosomic breech fetus also is an indication for cesarean delivery. Even with a favorable head–abdomen ratio at term, dystocia may be encountered with the delivery of either the fetal abdomen or after-coming head.

When the fetal head is extended, there is increased concern for the safety of delivery by either route. 8 , 33 A careful evaluation by radiograph or ultrasound should be a part of the predelivery examination of a patient with a breech fetus, regardless of the route of delivery chosen. 34 Extension of the after-coming head, diagnosed as an angle of greater than 105 degrees between the mandible and the cervical spine, may compromise the cervical spinal cord during delivery (see Fig. 1). Extension is uncommon (less than 5%) and may result from fetal goiter, a nuchal cord, or abnormalities of the shape of the uterine cavity. Additionally, extension may be caused by, or may be a sign of, fetal neurologic compromise, with an inability of the fetus to adequately flex his head on his chest. Extension should result in delivery by cesarean delivery. Extra care should be taken at cesarean delivery to cause the fetal head to flex during delivery by applying force on the fetal head during delivery. This ameliorates the tendency to fetal extension that occurs with the breech extraction used by some in a cesarean delivery. 35

Prolapse of the umbilical cord is decidedly rare in the first stage of labor. However, with single- and double-footling breech fetuses, the risk increases greatly during the second stage. Therefore, some authors exclude these specific types of breech fetuses from consideration for a trial of labor.

For the more common frank and complete types of breech presentation, the risk of cord prolapse is the same or only marginally greater than for a cephalic fetus. It is within this group, who constitute most breech fetuses at term, that a selective trial of labor will have the greatest benefit 36 ( Table 12 ).

Table 12. Selection characteristics for a trial of labor in a breech presentation

Measurement of the bony pelvis is performed to exclude borderline pelvic diameters. I advocate the use of radiologic measurement of the maternal bony pelvis. Computed tomography scan reliably measures pelvic dimensions and the attitude of the fetal head. Magnetic resonance imaging also has been successfully used in this setting. 37 The outcome of term breech delivery may be facilitated by only allowing a trial in women with pelvic measurements shown to be associated with successful breech delivery. 38 Todd and Steer, 6 in reviewing more than 1000 breech deliveries at term, demonstrated a critical difference in perinatal outcome when the pelvic inlet measured greater than 12 cm at the transverse of the inlet, and greater than 11 cm for the AP diameter. Gimovsky and associates 38 expanded this to include a midpelvic diameter of greater than 10 cm ( Table 13 ). Several authors have demonstrated the efficacy of this measure. 39 The use of computed tomography scanning results in a limited exposure of the fetus to ionizing radiation. 40 An additional benefit is the reproducibility and ease with which pelvic measurements may be obtained.

Table 13. Results of X-ray pelvimetry in a group of women undergoing a successful trial of labor under protocol

Typically, three views are obtained (Fig. 6). Because most patients will have undergone a failed attempt at ECV, I obtain pelvimetry at that time for the patient selected for a trial of labor. Patients in whom we are unable to convert a breech presentation are unlikely to undergo spontaneous conversion. Alternatively, pelvimetry may be obtained on presentation in early labor.

MANAGEMENT OF LABOR AND DELIVERY

When a trial of labor is undertaken with a breech-presenting fetus, it is crucial for an expedited cesarean delivery to be continuously available. The usual indicators of fetal well-being, as well as the adequacy of the progression of labor, will give rise to the indication for cesarean delivery on occasion. The criteria clinically used in supervising the labor of a cephalic fetus should be applied to the selected term breech fetus. In my experience, as well as others, cervical ripening, oxytocin induction, and partographic analysis of labor are safe and efficacious. Augmentation, when indicated, should call for a thoughtful re-evaluation of all aspects of the situation. For example, is the fetal size less than 4000 g? Has descent occurred progressively during the second stage? Have adequate maternal expulsive efforts failed to effect “crowning?” Oxytocin augmentation should be used only after an internal pressure transducer indicates inadequate contractions. Cesarean delivery should be used liberally in all other circumstances.

Fetal surveillance during labor and delivery should be continuous. After spontaneous rupture of membranes, internal monitoring may be used. Fetal heart rate patterns, particularly in the second stage of labor, may have pronounced variable decelerations. In breech labor and delivery, compromise to the umbilical circulation may be more frequent but generally is without sequelae. In addition, the intensity and duration of vagal stimulation with its concomitant effects on the fetal heart rate is different than in cephalic labor and delivery. Study of acid–base status at birth demonstrates a tendency to respiratory acidosis in breech vaginal delivery. This might explain a greater proportion of infants with lower Apgar scores at 1 minute. However, the base deficit in these infants generally is within the normal range. 41

Anesthesia considerations dictate the usefulness of regional anesthesia, as opposed to earlier approaches that used a combination of local and general techniques. As shown by Crawford, 42 regional anesthesia prevents premature maternal expulsive efforts, which should enhance the safety of delivery ( Table 14 ).

Table 14. Effect of anesthesia on breech delivery

(Adapted from Weingold AB: The Management of Breech Presentation. In Iffy L, Charles D [eds]: Operative Perinatology, pp 537–553. New York, Macmillan, 1984)

The second stage of labor should be managed under double-setup conditions. A gowned and gloved assistant, as well as anesthesia and pediatrics personnel, should be present. The patient should be instructed and encouraged to push effectively. The fetal heart rate should be continuously monitored. A nullipara should be allowed to push for up to 2 hours, a multipara up to 1 hour. If delivery is not imminent, cesarean delivery should be performed, the diagnosis being a failure of descent.

After lateral flexion of the trunk, the anterior hip is forced against and underneath the symphysis. Expulsion follows, with delivery of the anterior and then the posterior buttock. During “crowning,” an episiotomy should be performed to facilitate delivery.

Using a modified Bracht maneuver, a warm wet towel is placed around the fetal abdomen, and the fetus is grasped on the posterior aspect of the fetal pelvic girdle with care to avoid the fetal kidneys and adrenal. A gentle downward traction is exerted.

After the buttocks are fully expulsed, the back is born by rotation anteriorly. This allows the shoulders to enter the pelvis in the transverse diameter of the pelvic inlet. If there is a failure of anterior rotation, the fetus will be born as a posterior breech, and the sequence of maneuvers used to help in delivery will differ as appropriate.

As the anterior shoulder is seen at the introitus, the operator sweeps the right humerus across the infant's chest. Gentle rotation allows for the posterior shoulder and humerus to be born, completing the Løvset maneuver (Fig. 7).

With the infant delivered to the umbilicus, some authors recommend the use of uterine relaxants to facilitate the remainder of the delivery. The use of general anesthesia with halothane has been supplanted by parenteral betamimetics. We have used small aliquots of intravenous nitroglycerin for this purpose. 43 , 44

Delivery of the after-coming head follows with manual aid or forceps.

A Mauriceau–Smellie–Viet maneuver follows (Fig. 8). The fetus is placed abdomen down on the operator's right arm. The left hand supports the fetal neck. The index and middle fingers of the right hand are placed on the fetal maxilla to help maintain flexion of the head. The assistant may apply suprapubic pressure to expel the after-coming head (Naujok maneuver; Fig. 9). When delivery is further complicated by rotation of the fetal back posteriorly, a Prague maneuver allows for delivery of the occiput posterior breech variant.

Forceps may be used to facilitate delivery of the after-coming head (Fig. 10). Maintenance of head flexion is crucial. Traction is not required. The Piper forceps are specially designed for this task 45 and act as a class 1 lever. Because the fetal head is visible and should be aligned as in an occiput anterior position, any outlet forceps that may be applied as a simple pelvic application are indicated. Elliott forceps are particularly useful in this situation. Use of forceps may be helpful in a nulligravida or when the fetus is small and at term (less than 2500 g).

The infant then should be handed to the pediatrician in attendance. A segment of umbilical cord for acid–base analysis should be routinely obtained. Attention then can be directed to completion of the third stage of labor, as well as the repair of the episiotomy and genital tract lacerations.

A full dictated operative note should be completed at the time of delivery. The entire process of the labor, delivery, and immediate neonatal outcome should be referenced. Mention of each specific step is warranted, along with clinical observations regarding the relative ease or difficulty of the delivery process.

CESAREAN DELIVERY

Most breech-presenting fetuses will be born by cesarean delivery. Attention to the details of delivery are of no less consequence in this group.

When cesarean delivery is selected, the fetus should be evaluated before surgery using bedside ultrasound examination. A careful review of the fetus to diagnose extension of the head, the presence or absence of nuchal arms, and the location of the placenta should be made. Although estimates of fetal weight may be less accurate for breech-presenting fetuses, an estimated fetal weight should be made using a standardized formula. 46 Amniotic fluid volume and location of the umbilical cord also should be observed.

These observations may be important in understanding neonatal concerns after cesarean delivery. They allow both physician and patient to estimate the fetal condition just before birth. Important observations that have been confirmed before delivery include the presence of abnormal postures, broken bones, and the occasional transverse lie (or even an undiagnosed second twin).

Cesarean delivery should be expedited if the patient is in labor. Short-term tocolysis has been used so that the most appropriate anesthesia can be administered. Emergency cesarean delivery, with the greater risks of morbidity for both mother and child, should be chosen as a last resort.

The abdomen generally is opened with a transverse-type incision. Surgical choice of incision may vary by maternal habitus, prior surgery, or operator preference. Any incision may be used, as long as adequate visualization occurs and mobilization of the fetus is expedited.

Palpation of the uterus before the uterine incision should confirm the presentation. A low cervical transverse incision should be made carefully in the midline and extended to a depth necessary to expose the membranes. This is easier to do in practice if the membranes are intact. The important point is that the fetus may be incidentally incised if care is not taken. The infant born by cesarean delivery should be carefully examined after birth in this regard.

The fetus should be rotated (if necessary) so that the back is anterior before delivery. The assistant applies fundal pressure as the operator guides the buttocks up through the uterine incision. The use of force on the fundus allows the after-coming head of the breech fetus to remain in a flexed attitude. This approach also should minimize the loss of flexion of the fetal arms, which may result in a nuchal displacement.

A warm, wet towel is wrapped around the fetal abdomen to protect the fetus from traumatic injury and to mitigate against the onset of breathing movements before delivery.

Thus, by the use of an assistant giving fundal pressure, delivery of a breech fetus at cesarean delivery mirrors an assisted vaginal breech delivery. Avoid total breech extraction at cesarean delivery: it is inherently more of a risk to the fetus than an assisted or spontaneous breech delivery.

As with vaginal delivery, a section of umbilical cord should be sent for acid–base status. Attention is given to the description of the delivery process within the operative report.

PERINATAL OUTCOME

The most important factor in neonatal outcome for all infants is gestational age. This also is true for breech infants.

Many series, generally retrospective, some aided by meta-analysis, have studied the effect of mode of delivery on both immediate and long-term outcome. In the absence of congenital anomalies, laboring fetuses born ultimately by cesarean or vaginal delivery have similar outcomes, which are determined by gestational age and weight. Prolapse of the umbilical cord that occurs before hospitalization or goes unrecognized, although uncommon at term, plays a serious and compromising role for preterm infants. Such also is the case for prolapse of the fetal body through an incompletely dilated cervix. Entrapment of the after-coming head may have serious adverse consequences for the infant who likewise is preterm. This may occur at either cesarean or vaginal delivery.

Infants who are born immediately after admission to labor and delivery also have the greatest risk of asphyxia- and trauma-related injuries manifest in the immediate neonatal period. Women and their fetuses in whom breech presentation is not detected until labor, and who ultimately are delivered by cesarean delivery are subject to the greatest risk of maternal morbidity. 47

Regardless of the rate of cesarean delivery, breech infants have an increased risk of perinatal and neonatal morbidity and mortality. Cesarean delivery plays a role in decreasing but not eliminating this problem. Breech-presenting infants have higher rates of neurologic sequelae than their cephalic peers. The route of delivery plays little role in this difference. 48 .

The International Term Breech Trial 47 , 48 , 49 was undertaken to determine the best approach to term breech delivery management. This trial proved to be limited and controversial in several repects 49 and, subsequently, the PREMODA trial 50 was reported. With a much larger cohort studied, the authors determined that there was no difference in the neonatal outcome between vaginal and cesarean delivery in the term frank breech fetus. Consequently, the American College of Obstetricians and Gynecologists issued a revised Committee Opinion (#340, July 2006) concluding that with adaptation of strict protocol management and based on provider experience, a trial of labor for the term frank breech fetus was an acceptable option. 51 A Practice Bulletin from the Society of Obstetricians and Gynecologists of Canada in 2009 was in agreement with this selective approach to delivery management. 52  

The issues encountered in attempting to reach the optimal outcome for every pregnancy complicated by breech presentation include psychological, sociologic, and societal values. A strictly medical paradigm cannot perfectly fit each individual situation. Thus, a variety of approaches conform to the standard of care for medical practice. Resident training in breech delivery should include both the approach to delivery at cesarean section as well as vaginal delivery. 53 All parties involved must understand the risks and benefits of any suggested approaches. Because economic concerns have been emphasized more, a shift of decision making from the individual patient–physician pair to the consideration of the entire population has occurred. Both strategies must be made consistent.

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Breech, posterior, transverse lie: What position is my baby in?

Fetal presentation, or how your baby is situated in your womb at birth, is determined by the body part that's positioned to come out first, and it can affect the way you deliver. At the time of delivery, 97 percent of babies are head-down (cephalic presentation). But there are several other possibilities, including feet or bottom first (breech) as well as sideways (transverse lie) and diagonal (oblique lie).

Fetal presentation and position

During the last trimester of your pregnancy, your provider will check your baby's presentation by feeling your belly to locate the head, bottom, and back. If it's unclear, your provider may do an ultrasound or an internal exam to feel what part of the baby is in your pelvis.

Fetal position refers to whether the baby is facing your spine (anterior position) or facing your belly (posterior position). Fetal position can change often: Your baby may be face up at the beginning of labor and face down at delivery.

Here are the many possibilities for fetal presentation and position in the womb.

Medical illustrations by Jonathan Dimes

Head down, facing down (anterior position)

A baby who is head down and facing your spine is in the anterior position. This is the most common fetal presentation and the easiest position for a vaginal delivery.

This position is also known as "occiput anterior" because the back of your baby's skull (occipital bone) is in the front (anterior) of your pelvis.

Head down, facing up (posterior position)

In the posterior position , your baby is head down and facing your belly. You may also hear it called "sunny-side up" because babies who stay in this position are born facing up. But many babies who are facing up during labor rotate to the easier face down (anterior) position before birth.

Posterior position is formally known as "occiput posterior" because the back of your baby's skull (occipital bone) is in the back (posterior) of your pelvis.

Frank breech

In the frank breech presentation, both the baby's legs are extended so that the feet are up near the face. This is the most common type of breech presentation. Breech babies are difficult to deliver vaginally, so most arrive by c-section .

Some providers will attempt to turn your baby manually to the head down position by applying pressure to your belly. This is called an external cephalic version , and it has a 58 percent success rate for turning breech babies. For more information, see our article on breech birth .

Complete breech

A complete breech is when your baby is bottom down with hips and knees bent in a tuck or cross-legged position. If your baby is in a complete breech, you may feel kicking in your lower abdomen.

Incomplete breech

In an incomplete breech, one of the baby's knees is bent so that the foot is tucked next to the bottom with the other leg extended, positioning that foot closer to the face.

Single footling breech

In the single footling breech presentation, one of the baby's feet is pointed toward your cervix.

Double footling breech

In the double footling breech presentation, both of the baby's feet are pointed toward your cervix.

Transverse lie

In a transverse lie, the baby is lying horizontally in your uterus and may be facing up toward your head or down toward your feet. Babies settle this way less than 1 percent of the time, but it happens more commonly if you're carrying multiples or deliver before your due date.

If your baby stays in a transverse lie until the end of your pregnancy, it can be dangerous for delivery. Your provider will likely schedule a c-section or attempt an external cephalic version , which is highly successful for turning babies in this position.

Oblique lie

In rare cases, your baby may lie diagonally in your uterus, with his rump facing the side of your body at an angle.

Like the transverse lie, this position is more common earlier in pregnancy, and it's likely your provider will intervene if your baby is still in the oblique lie at the end of your third trimester.

Was this article helpful?

What to know if your baby is breech

What's a sunny-side up baby?

How your twins’ fetal positions affect labor and delivery

What happens to your baby right after birth

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 .

Ahmad A et al. 2014. Association of fetal position at onset of labor and mode of delivery: A prospective cohort study. Ultrasound in obstetrics & gynecology 43(2):176-182. https://www.ncbi.nlm.nih.gov/pubmed/23929533 Opens a new window [Accessed September 2021]

Gray CJ and Shanahan MM. 2019. Breech presentation. StatPearls.  https://www.ncbi.nlm.nih.gov/books/NBK448063/ Opens a new window [Accessed September 2021]

Hankins GD. 1990. Transverse lie. American Journal of Perinatology 7(1):66-70.  https://www.ncbi.nlm.nih.gov/pubmed/2131781 Opens a new window [Accessed September 2021]

Medline Plus. 2020. Your baby in the birth canal. U.S. National Library of Medicine. https://medlineplus.gov/ency/article/002060.htm Opens a new window [Accessed September 2021]

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Prenatal sonographic diagnosis of congenital anomalies

2 Prenatal sonographic diagnosis of congenital anomalies Eva Pajkrt, Lyn S. Chitty CONTENTS Routine ultrasound screening for fetal malformation The routine fetal anomaly scan Abnormalities in different systems Cranial and spinal abnormalities Cardiac abnormalities Pulmonary abnormalities Gastrointestinal abnormalities Urinary tract abnormalities Skeletal abnormalities Hydrops Fetal ultrasound is now an established part of standard obstetric care in many countries. It can be performed in early gestation and in the first, second and third trimester ( Table 2.1 ), as part of routine obstetric care, or as a targeted investigation in women at increased risk for a particular problem ( Box 2.1 ). In many countries fetal ultrasound is offered routinely both in the first trimester of pregnancy to establish the gestation and viability and again later (around 20 weeks) to examine the anatomy in more detail. Scanning earlier and later in pregnancy in most units tends to be performed on clinical indication rather than routinely. In this chapter we will confine further discussion to the use of fetal ultrasound for the detection of congenital abnormalities and genetic syndromes in the first and second trimesters of pregnancy. All anatomical systems will be described, but the focus will be on those areas that present for postnatal ultrasonography. Table 2.1 Use of obstetric ultrasound at different gestational ages. Gestational age in weeks BOX 2.1 Indications for detailed anomaly scanning Family or medical history • Previous abnormal child • Family history of abnormality/genetic condition • Maternal diabetes • Maternal epilepsy • Maternal medication (anti-epileptic, warfarin, lithium) • Maternal recreational drug use • ICSI pregnancy Risk factors developing in pregnancy • Increased nuchal translucency on 10–14 week scan • Raised maternal serum alfa-fetoprotein • Abnormality detected on routine scanning • Multiple pregnancy • Oligo- or polyhydramnios • Small or large for gestation age ICSI, intracytoplasmic sperm injection. ROUTINE ULTRASOUND SCREENING FOR FETAL MALFORMATION As congenital anomalies occur in 2–3% of all infants, detection, treatment and prevention of congenital anomalies are considered important goals of prenatal care. Routine screening for fetal structural anomalies has the potential to reduce perinatal mortality by elective termination of pregnancies complicated by serious congenital anomalies, to reduce morbidity by intrauterine treatment and to optimize management of delivery and early neonatal treatment. The ability of the ultrasound examination to detect fetal structural anomalies is central to the consideration of its clinical value, especially for anomalies detected before 24 weeks’ gestation. Despite the potential advantages of prenatal ultrasound examination, there is still much controversy about the value of ultrasound for routine fetal malformation screening. Studies report a considerable variation in the sensitivity, ranging from 20.7% to 82.4% in the first trimester ( Table 2.2 ) 1 – 6 and from 16.6% to 84.3% in the second trimester ( Table 2.3 ). 7 – 23 When interpreting this data it is important to differentiate between studies examining the use of routine fetal ultrasound as opposed to ultrasound used in a high-risk population where the investigation is targeted and detection rates are higher. 24 Furthermore, the sensitivity of ultrasound screening varies according to the nature and severity of the malformation, the gestational age of the fetus, equipment used, fetal position, maternal body mass index and the experience of the ultrasonographer. Many of the studies reported ( Tables 2.2 and 2.3 ) do not define these variables well. Finally, it must be remembered that the spectrum of abnormalities seen using prenatal ultrasound varies considerably from that seen postnatally. The prenatal sonographer will detect many lethal abnormalities (anencephaly, severe uropathies causing oligohydramnios and pulmonary hypoplasia, or complex cardiac anomalies) as well as anomalies that will be clinically silent in the newborn period and beyond (many renal anomalies, cystic lung lesions, or mild ventriculomegaly). The latter pose a difficult problem in defining optimum clinical management. Table 2.2 Summary of studies reporting the detection of fetal abnormalities before 14 weeks using routine ultrasound Table 2.3 Summary of studies reporting the detection of abnormalities before 24 weeks using routine ultrasound The routine fetal anomaly scan The Royal College of Obstetricians and Gynaecologists (RCOG) has issued guidelines for standards that should be applied for routine fetal anomaly scanning at 20 weeks’ gestation ( Table 2.4 ). Table 2.4 The routine fetal anomaly scan Structure Features examined Routine anomaly scan Extended views Head Skull shape Ventricles, cerebellum, cavum septum pellucidum Measure circumference and diameter   Face   Lips, nose Neck Observe and measure nuchal fold   Spine Longitudinal and transverse views   Heart Four-chamber view Left and right outflow tracts, aortic arch Thorax Diaphragm   Abdomen Stomach Cord insertion Kidneys and bladder Measure diameter   Limbs Three long bones in each limb Orientation of hands and feet Measure femur length Count fingers and toes From Guidelines for a routine fetal anomaly scan. London: Royal College of Obstetricians and Gynaecologists; 1997, 2001. The head is examined in the axial plane, and the skull shape and mineralization are checked. Measurements of the circumference (HC) and the width of the anterior horns and posterior horns of the lateral ventricles should be performed at the level of the cavum septum pellucidum and the third ventricle ( Fig. 2.1A ). The sub-occipitobregmatic view will demonstrate the posterior fossa with the cerebellum and cisterna magna ( Fig. 2.1B ). Figure 2.1 Axial views of the fetal head demonstrating (A) the view used to measure the head circumference, showing the anterior and posterior horns of the lateral cerebral ventricles, together with the cavum septum pellucidum. (B) The cerebellum (C), cisterna magna (*) and nuchal fold (NF) are seen in a slightly lower plane. The thorax is examined both in the longitudinal and axial planes. In the longitudinal view the hemi-diaphragms can be identified, with the stomach lying below the diaphragm and the heart above ( Fig. 2.2 ). In the axial plane the four-chamber view of the heart can be examined and should occupy one-third of the fetal chest ( Fig. 2.3 ). Figure 2.2 Longitudinal view through the fetal thorax in which the stomach (S) can be seen lying below and the heart (H) lying above the diaphragm. Figure 2.3 Axial view through the fetal chest showing the orientation and four chambers of the heart. The right side lies anterior (RA, right atrium; RV, right ventricle). The abdomen is examined in the axial plane at the level of the stomach and the portal sinus of the liver for its shape and contents, and the circumference (AC) is measured at this level. A baseline AC measurement should be obtained in case growth failure is suspected later in pregnancy. The abdominal cord insertion is examined to exclude anterior abdominal wall defects. The kidneys ( Fig. 2.4 ) and bladder are identified. The anteroposterior (AP) diameter of the renal pelvis should be measured and should normally be less than 5 mm. The perivesical arteries can be identified running around the bladder. Figure 2.4 Ultrasound image at 19 weeks’ gestation showing normal fetal kidneys in the coronal plane. Note the renal pelvis (*). The spine should at the very least be examined in the sagittal and axial planes and, if possible, in the coronal plane ( Fig. 2.5 ). In the axial plane the three ossification centers should be identified, with their skin covering, and should be seen to widen in the cervical region and narrow at the sacrum. In the sagittal plane ( Fig. 2.5A ) the normal curvature of the spine can be seen, with the upward sweep of the sacrum. Again the skin covering should be identified and the alignment of the laminae and vertebral bodies should be identified. In the coronal plane ( Fig. 2.5B ) the alignment of the transverse processes and laminae give a railway track appearance of the spine, which widens at the head and narrows towards the sacrum. In this view the alignment of the ribs can also be seen. With increasing resolution of modern ultrasound machines the spinal cord and cauda equina can be demonstrated ( Fig. 2.5C ). Figure 2.5 Standard views of the spine which should be examined in the axial, (A) sagittal and (B) coronal planes. (C) The spinal cord and cauda equinae (arrow) can often be seen using modern ultrasound equipment. The presence of three bones in each limb as well as hands and feet should be confirmed, although there is no expectation that fingers and toes should be counted at a routine scan. The femur length is measured, as again this gives a good baseline measurement for later comparison when growth restriction may occur. It also enables early detection of many major skeletal dysplasias. If time and resources exist, the fetal face should be examined to check the integrity of lips and nose, orbits, lens, and symmetry of the face. Anomalies of the palate are difficult to see, because of shadowing from surrounding bony structures. Examination of the fetal profile can be useful in the detection of micrognathia. Finally, fetal gender can be examined and, when requested, revealed to the parents. Using this protocol around 80–85% of severely handicapping or lethal abnormalities and varying proportions of other anomalies should be detected ( Table 2.5 ). Table 2.5 Rate of detection (%) of fetal abnormalities before 24 weeks’ gestation, using different screening protocols Ultrasound markers of fetal aneuploidy One group of cases that may not present to the postnatal sonographer are those associated with major chromosomal anomalies, since many of these conditions are lethal. In view of the high incidence (around 14%) of chromosomal disorders in structurally abnormal and growth retarded fetuses, karyotyping is discussed in most cases following the detection of most major and some minor anomalies or so-called soft markers ( Table 2.6 ). This is particularly recommended when more than one abnormality or marker is seen, as the incidence of aneuploidy increases from less than 2% in fetuses with isolated defects to 29% in those with multiple anomalies. 25 Table 2.6 Sonographic findings in common chromosome anomalies Fetal Doppler Intrauterine growth restriction (IUGR) occurs in 5–10% of all pregnancies and increases the risk of hypoxemia and acidemia, possibly resulting in perinatal death or significant morbidity in adult life. 26 Fetal weight can be estimated using a formula incorporating a combination of sonographic fetal measurements, usually HC, AC and femur length. A fetus with a weight below the 10th centile is defined as small for gestational age, but not necessarily growth restricted. The use of fetal and maternal Doppler has helped in making the prenatal distinction between constitutionally small fetuses, those that are small because of an underlying genetic etiology, and those where placental insufficiency (IUGR) is the cause. The interpretation of the hemodynamic changes in various fetal arterial and venous waveforms demonstrated by Doppler ultrasound make it possible to focus on the fetoplacental circulation and to evaluate the condition of the growth-restricted fetus. The umbilical artery was the first vessel to be evaluated by Doppler velocimetry. In normal fetuses a progressive rise in the end-diastolic velocity and subsequent decrease in pulsatility index can be demonstrated with advancing gestation. In IUGR fetuses an increase in pulsatility index can occur. With progressive deterioration of the fetoplacental circulation the umbilical artery waveform will change, showing absent or reversed end-diastolic blood flow. Growth-restricted fetuses with abnormal umbilical waveforms often have a poorer perinatal outcome than those with normal waveforms. 27 There is a direct correlation between umbilical artery Doppler and changes in the diastolic and mean blood flow velocity in the middle cerebral artery (MCA). During fetal hypoxia a pathophysiological adaptation occurs which results in preferential perfusion of vital organs. In the fetal brain this results in decrease in pulsatility index in the MCA as a direct consequence of vasodilation, 28 also referred to as redistribution or the ‘brain-sparing effect’. Besides the brain, the myocardium is also spared (the ‘heart-sparing effect’), leading to abnormal velocimetry of the aorta and inferior vena cava. 29 Doppler velocimetry has been applied to a variety of other fetal arteries and veins. Recent studies provide evidence that increased pulsatility index in the ductus venosus seems to be closely related to the presence of metabolic acidemia. 30, 31 These studies furthermore provide evidence that IUGR fetuses develop changes in Doppler velocimetry in a time-dependent, progressive sequence. Increase in umbilical artery pulsatility index occurs first, followed by a decrease in MCA pulsatility index. When the fetus becomes further hypoxic this will lead to Doppler changes in ductus venosus and aortic flow. The clinical utility of these Doppler changes in optimal timing of delivery in IUGR fetuses remains to be established. On the maternal side of the fetal circulation the flow in the uterine arteries is used as a screening tool, at 24 weeks of gestation, for placental insufficiency likely to result in pre-eclampsia or IUGR. 32 Abnormal changes in the uterine artery waveform are characterized by increased impedance indices and ‘notches’ in the waveform. Patients displaying abnormal uterine artery waveforms should be seen at regular intervals for monitoring of maternal wellbeing and fetal growth. Beside its usefulness in IUGR fetuses, assessment of Doppler changes in the MCA is becoming an accepted non-invasive method for diagnosis of fetal anemia in red blood cell alloimmunized pregnancies. Among fetuses at risk for immunological hydrops, 25% will need intrauterine transfusions. Up to 40% of the remaining group will develop mild to moderate anemia and hyperbilirubinemia postnatally, requiring phototherapy. In uncomplicated pregnancies the blood velocity in the cerebral vessels increases with advancing gestation. An increased MCA peak systolic velocity above 1.5 multiples of the median will identify 88% of those fetuses requiring intrauterine transfusion. 33 ABNORMALITIES IN DIFFERENT SYSTEMS Cranial and spinal abnormalities Many intracranial abnormalities are detectable at the time of the routine 20-week scan. One of the most common findings is that of choroid plexus cysts (CPCs), which occur in 1–2% of all fetuses. These can be uni- or bilateral, single or multiple ( Fig. 2.6 ). More than 95% resolve spontaneously before 26 weeks’ gestation. When seen with other soft markers, sonographic abnormalities or other risk factors for aneuploidy, such as maternal age ≥ 36 years or positive maternal serum screening, they may be associated with trisomy 18. They are not associated with any other adverse outcome. In the vast majority of cases CPCs are a benign transient finding with no clinical significance. 34 Other major abnormalities such as holoprosencephaly, anencephaly and posterior fossa cysts ( Fig. 2.7 ) may be detected at the time of a routine first or second trimester scan. However, unfortunately, many of the sonographic signs associated with other intracerebral anomalies develop later in pregnancy and are thus less amenable to detection in the second trimester. These include many, but not all, cases of hydrocephaly, microcephaly, agenesis of the corpus callosum, arachnoid cysts ( Fig. 2.8 ) and tumors. Many intracerebral abnormalities will therefore only be detected if the scan is initiated because of a clinical indication later in pregnancy, 10 whereas detection of anomalies such as anencephaly approaches 100% in the first 35 and second trimesters (see Tables 2.2 and 2.3 ). Figure 2.6 Unilateral choroid plexus cyst (*). Figure 2.7 Image taken at 19 weeks’ gestation showing a Dandy–Walker malformation. The cerebellar vermis is absent, the cerebellar hemispheres (C) separated, and a dilated fourth ventricle (4V) occupies the posterior fossa. Figure 2.8 A fetal head showing a single large arachnoid cyst. One of the most common serious congenital anomalies is open neural tube defect ( Fig. 2.9 ). Open spina bifida can be identified by examination in all three planes ( Fig. 2.5 ), sometimes just by loss of alignment of the vertebral bodies and absence of skin covering, but in more severe cases by identification of gross kyphoscoliosis. The diagnosis can be particularly difficult if the fetus is in the breech position, and low sacral lesions are readily overlooked. Identification of the cranial signs associated with spina bifida has resulted in a significant improvement in the diagnosis of this lesion, as the head is readily examined. In the presence of spina bifida the skull has a lemon shape in 98% of cases when scanned before 24 weeks, whilst the cerebellum is banana shaped in 72% ( Fig. 2.10 ). 36 These signs are also seen in 1% of normal fetuses. 37 Ultrasonographic detection of open neural tube defects compares favorably with maternal serum alfa-fetoprotein (MSAFP) measurements, which can identify around 80% of fetuses with spina bifida. Figure 2.9

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Sonographic assessment of placental location: a mere notional description or an important key to improve both pregnancy and perinatal obstetrical care? A large cohort study

Salvatore gizzo.

1 Department of Woman and Child Health-University of Padua, Padua, Italy

Marco Noventa

Amerigo vitagliano, michela quaranta.

2 Department of Obstetrics and Gynaecology, University of Verona, Verona, Italy

Valentina Di Giovanni

Shara borgato, carlo saccardi, donato d’antona.

During a standard obstetrical sonogram, the assessment of placental location (PL) is often limited to a mere notional description without formulating any association to possible implications on pregnancy and childbirth. The aim of the study was to speculate if different sites of PL may have a role in influencing fetal presentation-(FP) at birth and if certain pregnancy-complications may be more closely associated with one rather than with another PL. We conducted an observational-prospective-cohort study on pregnant women referred to the Ob/Gyn Unit of Padua University for routine third-trimester ultrasound scan. For all eligible patients we evaluated the correlation between sites of PL and perinatal maternal/fetal outcomes. Non-cephalic presentation was found in 1.4% of anterior, 8.9% of posterior, 6.2% of fundal and 7.2% of lateral insertions. FP at the beginning of the third trimester as opposed to presentation at birth was concordant in 90.3% of anterior, 63.3% of posterior and 76.5% of lateral insertions. Considering only non-cephalic fetuses we observed a decreasing probability for spontaneous rotation in the following lies: 88% anterior-PL, 80% posterior-PL, 77% lateral-PL, and 70% fundal-PL. Patients with posterior-PL (significantly associated with previous-CS) had a significantly higher CS-rate (due to previous-CS and breech-presentation). Significant differences were found in terms of gestational-hypertension and fresh-placental-weight between different sites of PL. In conclusion our data showed that an understanding of the role that PL plays in influencing the incidence of certain maternal-fetal conditions may assist Clinicians in improving perinatal maternal/fetal outcomes.

Introduction

Ultrasound imaging has become an integral component of routine prenatal medical care for most pregnant women. During an obstetrical ultrasound, evaluation of the fetus is chief priority but often, the other components (placenta, umbilical cord, and amniotic fluid) which represent an integral part of gestation, are arguably not given the attention they deserve [ 1 ].

Both the American College of Obstetricians and Gynecologists and the American Institute of Ultrasound in Medicine recommended that the standard obstetric sonogram in the second and/or third trimester should include the evaluation of placental position and morphology, the estimation of amniotic fluid volume, and the evaluation of both the morphology and function of the umbilical cord [ 2 , 3 ].

While abnormalities in amniotic fluid volume and umbilical cord Doppler velocimetry immediately alert the sonographer (possible implications on the continuation of physiological pregnancy), sonographic assessment of placental location (PL), after exclusion of previa or marginal insertion (necessary to assess the option of vaginal delivery), is often limited to a mere notional description without any link to possible implications on pregnancy and childbirth [ 4 - 6 ].

There is a relative paucity of data regarding PL and subsequent pregnancy and delivery outcomes. Furthermore, studies of its association with specific obstetric complications have reached contradictory conclusions and no consensus has yet been achieved regarding the relationship between PL and non-vertex fetal presentation (FP) at term [ 7 , 8 ].

We would speculate whether different sites of PL may have a role in influencing FP at birth and if some pregnancy complications may be more closely associated with one rather than with another insertion site.

Materials and methods

In the period between January-2012 and September-2013 we conducted an observational prospective cohort study on pregnant women referred to the Ob/Gyn Unit of Padua University for routine third trimester scan (gestational age 29-31 weeks).

Our Study was defined exempt from IRB after consultation of the local ethical committee. Approval from the local Institutional review board for health sciences is not required for observational/retrospective studies in which clinical and/or surgical management is not modified by the investigators. All patients were properly counselled regarding the aim of the study and gave written informed consent for the use of their data in respect to privacy law (Italian Law 675/96).

We considered eligible for the study single fetus pregnancies having complete clinical records of all antenatal visits beginning from the first trimester and defined as uncomplicated upon recruitment, patient proficiency in Italian language and with an expressed intention to continue pregnancy care until delivery at our Clinic.

We excluded patients with incomplete clinical records and those who did not deliver at our Unit or dropped-out of the follow up program. We also excluded pregnancies with a maternal history of pre-gestational diabetes [ 9 ] and/or hypertension [ 10 ], patients on dietary calcium supplementation due to an estimated increased risk for preeclampsia [ 11 , 12 ], history of previous uterine surgery (including both the cervix and corpus uteri), with the exception of uncomplicated cesarean section (CS), [ 13 - 18 ], patients who chose VBAC (vaginal birth after cesarean) or attempted external cephalic version [ 19 - 21 ], placenta previa, abnormalities in amniotic fluid volume (oligo and polihydramnios) and estimated fetal weight greater than 75° or lower than 25° centile. Patients participating in a concurrent study conducted at our Clinic regarding alternative maternal positions during labor were not included [ 22 ].

Intervention

A standard ultrasound was performed on all eligible patients at the beginning of the third trimester of pregnancy (29-31 gestational weeks) and at term (38 gestational weeks). Patients who delivered preterm were evaluated sonographically upon delivery room admission.

The ultrasound examination was performed by one of the researchers (SG) previously trained in the use of intrapartum ultrasound. The trans-abdominal scan was performed in maternal supine position with a 3.5 MHz convex probe AB2-7-RS ( Voluson e6 compact-GE Healthcare, GE Medical Systems Ltd, Hatfield, AL9 5EN ).

Data collection

Data regarding maternal features (age, parity, mode of delivery in previous pregnancies, pre-gestational BMI, weight gain during pregnancy) was collected for all patients.

At recruitment, the following data was entered into a computerized database: spontaneous or assisted conception, gestational age, FP and eco-biometry, placental location (anterior, posterior, lateral, or fundal) and amniotic fluid index.

Following delivery, data regarding gestational age, third trimester pregnancy complications (gestational diabetes, hypertension/preeclampsia, threat of preterm birth, placental abruption, pPROM, preterm birth), fetal presentation, mode of delivery (vaginal spontaneous or operative, cesarean section elective or urgent), length and complications of the third stage of labour (for vaginal delivery alone) was collected for all patients included in our study.

We also considered neonatal sex, weight, umbilical pH values and necessity of intensive care.

Finally, we completed the dataset by recording information concerning placental fresh weight and macroscopic features (regular, bilobed, succenturiate lobed, circumvallate/circumarginate, velamentous cord insertion).

Primary endpoint was to evaluate the existence of a correlation between sites of PL and FP at birth.

Secondary endpoint was to evaluate if specific sites of PL were associated with spontaneous cephalic version before delivery in the cohort of patients with non-cephalic FP observed sonographically at the beginning of the third trimester of pregnancy.

Finally, we investigated possible correlations between the site of PL and maternal features (age, parity, smoking habits, pre-conceptional BMI, type of previous delivery), characteristics of pregnancy (spontaneous or assisted conception, pregnancy weight gain, gestational age at delivery, third trimester complications), delivery and neonatal outcome (mode of delivery, third stage complications, neonatal features and well-being at birth, placental weight and morphology).

Statistical analysis

Statistical analysis was performed by SPSS software (Chicago, IL) for Windows version 19, applying parametric and non-parametric tests when appropriate. The Kolmogorov-Smirnov test was used to assess the normality of distribution. Continuous variables were expressed as absolute numbers, average ± standard deviation, and analyzed by Student-t test or Anova test when appropriate; categorical variables were expressed as percentages and analyzed through the χ 2 test or the Fisher’s exact test, when appropriate. Statistical significance was defined as P values <0.05.

In the time interval considered, 1056 patients satisfied the inclusion criteria and were enrolled in the study. Collected data pertaining to maternal epidemiological features and pregnancy characteristics at recruitment was reported in detail in Table 1 by stratifying the single variables for placental site. ( Table 1A , ​ ,1B 1B ).

Data about maternal epidemiological features (A) and pregnancy characteristics at recruitment (B) stratified for all sites of placenta insertion

The mean gestational age at birth was 38.7 ± 1.3 weeks. Regarding the mode of delivery, 51.9% (548 patients) delivered spontaneously, 5.2% (55 patients) by operative vaginal delivery, 19.4% (205 patients) by elective-CS and 23.5% (248 patients) by urgent-CS.

The indications for CS (453 cases) were the following: previous-CS in 41.5%, breech presentation in 9.7%, abnormal fetal-heart-rate in 34.9%, and dystocia in 13.9%.

Considering vaginal delivery (603 cases), the duration of the third stage was inferior to 60 minutes in 99.2% of labors while 5 cases required manual removal of the placenta.

Concerning newborn characteristics, 54.5% were male and 45.5% were female, mean birth weight was 3300.2 ± 446.5 g, mean umbilical pH value was 7.28 ± 0.1 and only 0.3% required (32 cases) intensive care.

The mean value of fresh placental weight was 611.76 ± 116.82 grams. Histological evaluation of the placenta showed regular findings in 99.9% with structural abnormalities observed in only 12 cases (0.1%) (8 velamentous and 1 marginal cord insertions, 2 bilobed and 1 succenturiate placenta).

The correlation of data regarding the site of PL and FP at birth showed significant statistical differences between anterior and non-anterior insertions.( P <0.05). In detail, pregnancies with an anterior PL had a 1.4% of non-cephalic fetuses (8/579 pregnancies, all breech presentations) as opposed to 8.9% (29/327 pregnancies, 7.9% breech and 1.0% transverse presentations) in posterior, 6.2% (5/81 pregnancies, all breech presentations) in fundal and 7.2% (5/69) in lateral insertions ( Figure 1A ).

Correlation of data regarding site of placenta insertion and fetal presentation observed at birth (A), at the beginning of the third trimester (B), Δ variation of non-cephalic presentation and the estimation of the probability of spontaneous rotation (C).

Similarly, the correlation of data regarding placental site and FP observed at the beginning of the third trimester showed a statistically significant difference between anterior and non-anterior locations. ( P <0.001). The percentages of non-cephalic fetal presentations according to placental lie are the following: 11.1% (64/579 pregnancies with 54 breech and 10 transverse presentations) of anterior, 44.3% (145/327 pregnancies, 134 breech and 11 transverse presentations) of posterior, 29.6% (24/81 pregnancies, 23 breech and 1 transverse presentations) of fundal and 31.9% (22/69 pregnancies, 18 breech and 4 transverse presentations) of lateral insertions ( Figure 1B ).

In comparing data regarding FP at the beginning of the third trimester as opposed to presentation at birth, we observed that in anterior PL fetal presentation was concordant in 90.3% of cases while in posterior and lateral insertions the concordance dropped to 63.3% and 76.5% respectively ( P <0.001).

Considering only non-cephalic fetuses, after stratification of data according to spontaneous cephalic version at birth in relation to PL, we found a statistically significant decreasing probability for spontaneous cephalic version in the following placental locations: 88% in anterior, 80% in posterior, 77% in lateral, and 70% in fundal insertion sites ( P <0.05) ( Figure 1C ).

Considering maternal obstetrical history, we found a significant association between previous CS and posterior PL in the following pregnancy. ( P <0.05). In the cohort of patients who delivered by CS we observed a posterior PL in 37.1% versus 25% observed in the cohort of those who delivered vaginally. Additionally, patients with posterior PL showed a significantly higher rate of CS when compared to those with PL in different uterine sites (27.5% versus 18.6%, respectively). ( P <0.01) As expected, patients with a posterior PL had a significantly higher rate of CS with the indication of status post CS (51.7% versus 41.7%, respectively) and breech presentation (17.7% versus 10.4%) as opposed to those with a non-posterior insertion site ( P <0.05) ( Figure 2 ).

Stratification of data regarding Cesarean Section rate according to the indication for all the sites of placental insertion.

Considering pregnancy outcome in relation to PL, we found significant differences only in the diagnosis of gestational hypertension which was identified in 5.5% of posterior insertions, 3.1% of anterior insertions, 1.2% of fundal insertions and no cases observed in pregnancies with a lateral insertion ( P <0.05).

Finally, significant differences were also found in terms of fresh placental weight, with the highest weight detected anteriorly (mean value 632.22 ± 112.39 grams) and the lowest posteriorly (mean value 582.56 ± 121.08) ( P <0.05) ( Figure 3 ).

Stratification of data regarding fresh placental weight according to the sites of placental insertion.

No other significant differences were found when comparing the remaining maternal epidemiological features, pregnancy characteristics, delivery trends, and neonatal outcomes.

Advances in technology and the development of real-time three/four dimensional ultrasonography has initiated a new era in obstetrical diagnosis. The visualization of in-utero fetal activity during the various stages of gestation may help Perinatologists comprehend the existing relationships between fetal behavior and neurological development and maturation [ 23 ].

Speculations regarding the role of PL in determining FP at birth as well as the impact that the different sites of PL may have on pregnancy development may be considered by the majority of Obstetricians as anachronistic and of little value.

Although PL has been systematically included in standard ultrasound reports for the past 30 years, unfortunately, only few studies (frequently with contrasting results) have been conducted with the aim of investigating the impact of PL on pregnancy outcome (excluding research on low-lying placenta/placenta previa).

In the era in which “reducing the primary cesarean delivery rate represents a worldwide priority”, [ 24 , 25 ] an investigation focused on PL and its impact on fetal presentation at term should be considered relevant.

A very recent ACOG consensus strongly recommends offering pregnant woman with non-cephalic FP after 36 gestational weeks the option of external cephalic version [ 25 ].

Considering that our data, in agreement with the small number of available studies [ 26 - 28 ], clearly demonstrated that PL may have a strong impact on non-cephalic FP at birth, it may be appropriate that Obstetricians begin considering this information before counseling patients regarding birth plan.

Up until 24 gestational weeks, the frequencies of breech and cephalic presentations are equal within the longitudinal situs [ 29 ]. From the 25th to 36th week of gestation there is an increase in the frequency of cephalic presentation with a proportional decrease in breech presentation [ 29 ].

We may speculate that placental location may behave as an intrauterine factor potentially capable of influencing the physical conditions (gravity, maternal posture, fetal neurological development) that favor the fetal body axis posture that is manifested by cephalic presentation.

We found that, beginning in the third trimester of pregnancy, the anterior PL was associated with a significantly lower rate of non-cephalic presentation (11.1%) when compared to all the remaining locations with a rate ranging from 29.6% in fundal to 44.3% in posterior positions.

Despite the fact that the exact mechanisms involved in facilitating fetal rotation into cephalic presentation are not precisely understood, it has been postulated that the fetus performs a change of lie and presentation by sudden extension of the legs and active whole body movements (such as kicking), and perhaps by body rolling. All these actions require a certain degree of neuromuscular and sensorial maturation which is usually present by the end of the second trimester of pregnancy in the human species [ 29 ].

The possibility that certain sites of PL (anterior) rather than others (fundal, posterior, lateral) may favor early fetal alignment in cephalic presentation leads us to hypothesize on a possible placental intrauterine spatial hindrance effect. Likely the anterior site of PL is associated with a greater placental volume as opposed to other insertion sites, as indirectly demonstrated by our data which showed a significantly higher fresh weight in the anterior sites.

Stating that while this evidence requires further confirmation, it may be possible to hypothesize that fetuses with an anterior PL at the beginning of the third trimester may “passively” assume (by body rolling rather than by sudden extension of the legs and/or by kicking due to low fetal weight and immaturity of the central nervous system) the most convenient position as influenced by gravity.

In cephalic presentation the fetal upper body segments (the hypotonic-atonic part of the body) are in caudal direction while the lower body segments take a cranial position. In other words, assuming a cephalic presentation brings the body axis along the direction of gravity [ 29 ].

Our data clearly demonstrated that while only 11.1% of fetuses with anterior PL were found to be in breach presentation at the beginning of the third trimester of pregnancy, by delivery this cohort of fetuses had demonstrated the highest rate of spontaneous rotation into the cephalic position. This fact probably confirms the assumption that in the event of an anterior placental location, the most “spontaneous and natural” convenient behavior for the fetus is that of assuming cephalic presentation.

On the contrary, fetuses with posterior, fundal, or lateral PL, shift from breach to cephalic later in intrauterine life (around the first half of the third trimester of pregnancy). This fact might be explained by two theoretical assumptions: the first being that, when the placenta in located in a non-anterior site, the fetuses has the “need” to assume a “gravity position” later in gestation, the second is that in a non-anterior placental site, a cephalic positioning generally requires an “active” fetal involvement that depends on a higher degree of neuromuscular development typically reached in later stages of gestation.

The higher rate of non-cephalic fetuses at birth in non-anterior PL may be explained by the assumption that ongoing pregnancy in the third trimester is associated with a decrease in the rate of fetal weight gain and a reduction in amniotic fluid volume (frequently idiopathic), both factors which potentially reduce the likelihood of spontaneous rotation [ 4 ].

This assumption was indirectly confirmed by data recently reported in studies which evaluated the predictors of successful external cephalic version in non-cephalic fetuses [ 30 , 31 ].

We are aware of the fact that our speculations regarding the association between PL and FP in the third trimester of pregnancy warrant confirmation by further multicenter studies involving a very large cohort of patients.

Regarding the correlation between maternal epidemiological features and obstetrical history with specific PL, our data showed a significant association only between history of previous CS and posterior PL.

Our data further confirmed previous evidences by Naji et al. [ 32 ] demonstrating that the presence of CS scars in the uterine wall is associated with an increase in the number of posterior PL and a reduced number of implants in the fundal portion of the uterine cavity. Furthermore, the same study group demonstrated that the probability of miscarriage in the pregnancy following a CS is inversely associated with the distance between the uterine scar and the site of implantation [ 33 ]. This association of evidences leads us to consider if perhaps the detection of a significantly higher rate of posterior PL in pregnancies following CS may be due to a higher rate of pregnancy loss due to implantation near the uterine scar or simply due to a casual implantation in the posterior uterine wall.

Regarding the association between placental location and adverse pregnancy outcomes, our data, though collected on a large study population (1056 patients), failed to demonstrate any relationship as previously reported in literature [ 7 , 34 , 35 ].

Devarajan et al in 2012 reported that PL was not associated with differences in newborn weight or in any other perinatal outcome [ 36 ], while previously various Authors demonstrated that a posterior PL may be a contributory risk factor for stillbirth [ 33 ] and that pregnancies complicated by IUGR are significantly more likely than non-IUGR pregnancies to have lateral placentation [ 37 ].

In 2011 Fung et al analyzed 16236 patients to determine whether PL in the second trimester of pregnancy is associated with adverse pregnancy outcomes found that women with a ‘fundal’ placenta were at an increased risk of the following: pre-eclampsia, preterm delivery before 34 weeks, non-vertex presentation, small for gestational age fetuses and manual removal of the placenta following vaginal delivery. Likewise similar results were reported for lateral placentation. Authors therefore concluded that “non-central PL” in the second trimester is associated with an increased risk of adverse obstetric outcomes [ 7 ].

Unexpectedly, in our study group none of the patients with a lateral PL developed hypertension or preeclampsia versus an average 5% rate occurring in other insertion sites.

Regarding intrapartum outcomes, in addition to the differences observed in terms of FP between the different insertion sites, we found that in women with a posterior placenta the overall CS rate was higher than in the non-posterior sites. However this finding requires further investigation since this event may be affected by the bias linked to a higher rate of recurrent CS. As stated above, the cohort of patients with posterior placenta showed a higher rate of previous CS.

Excluding FP, incidence of gestational hypertension, and placental weight at birth, we did not find any differences between the various sites of insertion and pregnancy-related complications, intrapartum adverse events, neonatal wellbeing, and placental morphology.

Most likely our results were affected by a selection bias due to that fact that we defined as eligibility criteria for study inclusion an “uncomplicated pregnancy until the moment of recruitment” which occurred at the beginning of the third trimester of pregnancy.

Other potential bias may include: exclusion of patients with an estimated increased risk of developing preeclampsia and assuming dietary calcium supplementation, exclusion of patients assuming alternative positions during labor as well as the lack of data regarding the fetal occiput and spinal position before delivery which may influence the occurrence of intrapartum adverse events [ 38 , 39 ], and lack of consideration of differences in obstetrical history which may affect the overall rate of “recurrent CS” which indirectly influences the placental weight at delivery (typically heavier in CS as opposed to vaginal delivery, probably due to uterine contractions during labor which squeeze maternal blood from the placental parenchima) [ 40 ].

As points of strength we report: strict inclusion criteria, interesting findings regarding the impact of obstetrical history in determining the site of PL in turn responsible for the significant differences found in terms of FP at birth, the formulation of a possible explanation of the mechanism by which PL facilitates an earlier or later cephalic version of the fetus and the hypothesis of the important contribution that fetal neuromuscular development, dependent on the gestational age, has in the fetus assuming a cephalic or non-cephalic presentation.

In conclusion, considering the placenta as an “active and integral part of gestation” may help us comprehend the physiopathological mechanisms responsible for events previously considered as “casual or idiopathic”. In the modern obstetrical care setting in which new evidences are constantly set forth, the persistence in under-investigating and misunderstanding the potential impact that the various placental sites may have in influencing pregnancy, peri-partum and neonatal outcomes may be considered anachronistic.

We believe that comprehending the role that PL has in increasing or diminishing the incidence of certain maternal-fetal adverse events may allow us to decrease the number of pregnancy and perinatal conditions currently treated by symptomatic therapy or by an empirical approach.

Disclosure of conflict of interest

Imaging uterine lipoleiomyomas: A case series and review of the literature

Affiliations.

• 1 University of California, Irvine Department of Radiological Sciences, 101 the City Drive South, Orange, CA, 92868, USA.
• 2 University of California, Irvine Department of Pathology and Laboratory Medicine, University of California Irvine, School of Medicine, Irvine, CA, 92697, USA.
• PMID: 37305513
• PMCID: PMC10256895
• DOI: 10.1016/j.heliyon.2023.e15970

Background: Lipoleiomyomas are uncommon uterine lesions containing adipose and smooth muscle tissue. They have a variable presentation and are usually found incidentally on imaging or post-hysterectomy tissue analysis. Given their low prevalence, there is a dearth of literature describing imaging characteristics for uterine lipoleiomyomas. In this image-rich case series, we summarize an example of an initial presentation as well as present ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) findings for 36 patients.

Case presentation: We present the detailed clinical course of a representative patient evaluated for uterine lipoleiomyoma and describe imaging findings seen in another 35 patients. This includes ultrasound findings from 16 patients, CT findings from 25 patients, and MRI findings from 5 patients. Among the 36 total patients, symptoms at the time of diagnosis were variable but often included abdominal or pelvic pain; however, most patients were asymptomatic, and the lipoleiomyomas were incidentally discovered on imaging.

Conclusions: Uterine lipoleiomyomas are rare and benign tumors with variable presentations. Ultrasound, CT, and MRI findings can assist in diagnosis. Findings on ultrasound typically include well-circumscribed hyperechoic and septated lesions with minimal to no internal blood flow. CT shows fat-containing either homogeneous or heterogeneous circumscribed lesions depending on their ratio of fat and smooth muscle tissue. Lastly, on MRI, uterine lipoleiomyomas commonly appear heterogenous with loss of signal on fat-suppressed sequences. These imaging findings are highly specific for lipoleiomyomas, and familiarity with these findings may reduce unnecessary and potentially invasive procedures.

Keywords: Case series; Computed tomography; Diagnostic imaging; Magnetic resonance imaging; Pelvic neoplasms; Ultrasound; Uterine lipoleiomyoma.

© 2023 The Authors.

Publication types

• Case Reports