Breech Presentation Deformation

GENESIS

The frequency of singleton breech presentation at term is 3.1% and rises to 6.2% when multiple births are included. Breech presentation is an important cause of deformation, and fully one-third of all deformations occur in babies who have been in breech presentation ( Fig. 42.1 ). Because 2% of newborns have deformations, this indicates that 0.6% of neonates have one or more deformations due to breech presentation; therefore this topic will be given extensive coverage. Among infants born with deformations, 32% were in breech presentation (vs. 5–6% of normally formed infants), and 23% of malformed infants were also in breech presentation. Among 142 infants with spina bifida, 38% were in breech presentation and 68% of these infants had lower extremity weakness or paralysis. Among those infants with paralyzed legs, 93% manifested breech presentation; thus breech presentation becomes more likely with fetal inability to power the legs. Numerous fetal and maternal factors can lead to breech presentation and thereby increase the risk for adverse outcomes. Some of these factors include prematurity (25% breech), twinning (34% breech), oligohydramnios due to chronic leakage (64% breech), uterine malformations, placenta previa, maternal hypertension, and fetal malformations.

Breech presentation is more common in primigravida women, especially older primigravida women, presumably because of the shape of the uterus and the reduced space for fetal and uterine growth. The spatial restrictions associated with twinning also increase the likelihood of breech presentation, especially for the second-born. In a 2023 study of over 355,990 singleton pregnancies, breech presentation occurred 20% more often in singleton pregnancies conceived via both assisted reproductive technology (adjusted odds ratio: 1.20, 95% confidence interval: 1.10–1.30, P < .001) and ovulation induction (adjusted odds ratio: 1.21, 95% confidence interval (CI): 1.04–1.39, P < .05) than naturally conceived pregnancies. No significant associations were observed between the three modes of conception and transverse/shoulder or face/brow presentations. The prematurely born baby is also less likely to have shifted into the vertex birth position, and prematurity is more common with multiple births. Unless there is oligohydramnios or twinning, the premature fetus in breech presentation generally does not have associated deformations because there has not been sufficient constraint to cause molding. Furthermore, breech presentation can be considered normal with prematurity because at 32 weeks of gestation, 25% of all fetuses are in breech presentation; after this time, the majority of fetuses shift into vertex presentation. Any situation that causes oligohydramnios, whether it be chronic leakage of amniotic fluid or lack of urine flow into the amniotic space, will restrict movement and greatly increase the chance of the fetus being in breech presentation. Alterations in the size and shape of the uterine cavity may also increase the frequency of breech presentation. This may be secondary to uterine structural anomalies or myomas. The implantation and placement of the placenta may also be a factor, as 66% of placentas in breech delivery implant in the cornual-fundal region (vs. 4% of vertex presentations), whereas in 76% of vertex presentations, the placenta implants on the midwall of the uterus (vs. 4% of breech presentations).

Although the best mode of delivery for infants in breech presentation is controversial, most studies suggest that the risk for neonatal morbidity and mortality is increased when infants in breech presentation are delivered vaginally as opposed to via cesarean section. Delivery-related neonatal injury during cesarean delivery is more frequent in the reverse breech extraction method compared with standard vertex extraction. Traumatic injuries following vaginal delivery of breech infants can include fractures (clavicle, femur, humerus) dislocations, brachial plexus injuries, facial nerve injuries, cephalic hematomas, cerebral hemorrhages, bruising with hyperbilirubinemia, cervical cord injuries, cord prolapse, birth asphyxia, and testicular trauma. In most large series, these types of injuries occur less frequently with cesarean delivery, but in some recent series using modern delivery methods, the rate of such injuries is similar in planned vaginal breech delivery compared with elective cesarean section. In 2009, a study of 1345 term breech deliveries found no statistical difference in low 5-minute Apgar scores and arterial cord blood pH between vaginal delivery and cesarean section, although there were higher rates of severe plexus injuries and two neonatal deaths after a trial of labor whereas no perinatal deaths of a term breech infant in the cesarean group. In a 2005 study of 1433 breech infants, Pradhan et al. compared the outcome of infants born by prelabor cesarean section with those delivered vaginally or by cesarean section in labor and found that those in labor were significantly more likely to have low 5-minute Apgar scores (0.9% vs. 5.9%, P < .0001) and require admission to the neonatal unit (1.6% vs. 4%, P = .0119). Despite the these differences, there was no significant difference in long-term morbidity between the two groups and no difference in rates of cerebral palsy. These and many other studies have led some authors to suggest that with a normal pelvis and normal term birth weight, assisted vaginal breech delivery by an experienced obstetrician may be as safe as cesarean section delivery. However, a 2022 metaanalysis assessing the maternal and fetal risks of planned vaginal breech delivery versus planned cesarean of 94,285 births found that the relative risk of perinatal mortality was 5.48 (95% CI: 2.61–11.51) times higher in the vaginal delivery group, 4.12 (95% CI: 2.46–6.89) for birth trauma, and 3.33 (95% CI: 1.95–5.67) for Apgar results. Maternal morbidity showed a relative risk 0.30 (95% CI: 0.13–0.67) times higher in the planned cesarean group. Clinical practice guidelines for vaginal delivery of a breech presentation were published in 2006 by the American College of Obstetricians and Gynecologists and in 2009 by the Society of Obstetricians and Gynaecologists of Canada.

Because of the risk of cervical cord injuries with vaginal delivery, most studies have relegated breech infants with hyperextended heads for automatic cesarean section. Trials of vaginal delivery have succeeded in 60% to 70% of patients, without significant differences in outcome measures for primiparas versus multiparas or for frank versus non-frank breech presentations. In North America, 70% to 80% of all women with breech presentation deliver by cesarean section (with similar trends observed in other parts of the world), so obstetric resident training experience with vaginal breech deliveries may be insufficient to guarantee sufficient expertise.

Breech presentation shows a familial tendency, and 22% of multiparous women delivering a breech infant had previously experienced a breech delivery. If the first infant in a family is breech-born, there is a 9.4% chance the second child will be breech-born; whereas if the first child is vertex, there is only a 2.4% chance the second will be breech (this being the background risk for breech delivery). Women with recurring breech presentation have a lower risk of adverse perinatal outcome, possibly due to increased attention to perinatal care. The familial tendency toward breech deliveries may be related to inherited uterine structural characteristics (see Chapter 45 ), or it may be a consequence of a genetic neuromuscular or fetal malformation syndrome such as myotonic dystrophy. Presumably, the lower risk of adverse perinatal outcome relates to detection of maternal anatomic abnormalities (or fetal genetic abnormalities) that might result in closer follow-up during subsequent pregnancies.

In about 70% of fetuses in breech presentation, the legs are extended in front of the abdomen ( Fig. 42.2 ). Once the movements of the fetus become limited by extension of the legs in front of the abdomen, the fetus has less chance of extricating itself from the breech presentation, and Dunn has used the analogy of the “folding body press” wrestling hold. Once a wrestler has an opponent in a position with the legs in front of the abdomen, there is little the opponent can do to escape. Breech presentation with the hips flexed and knees extended is termed frank breech (see Figs. 42.2 and 42.3A and D ). When the hips and knees are flexed, it is called complete breech ( Fig. 42.3C ), and when the hips and knees are extended, it is referred to as to the footling breech , as depicted in Fig. 42.3B . With modern methods of delivery, the particular type of breech presentation appears to have no significant effect on adverse outcomes associated with the mode of delivery, despite that cord prolapse occurs much less frequently with frank breech presentation (0.4%) versus complete breech (4–10.5%) or footling breech presentation (15–28.5%).

FEATURES

Prolonged breech position in late fetal life gives rise to increased uterine fundal pressure and molding of the fetal head, which may become retroflexed. This type of constraint results in anteroposterior elongation of the head (dolichocephaly) with a prominent occipital shelf, the so-called “breech head” ( Fig. 42.4 ). In cases of ultrasonographic biometric discrepancy between biparietal diameter and femur length, the fetal position should be taken into account. The shoulders are often thrust under the lower auricle, and the mandible may be distorted. The legs may be caught in front of the fetus, which tends to dislocate the hips and, occasionally, causes genu recurvatum of the knee and often calcaneovalgus position of the feet. In the frank breech position, with the legs flexed across the abdomen, the feet are likely to be compressed into a calcaneovalgus position, whereas in the complete breech position with the knees flexed, equinovarus foot deformation may develop. The genital region, as the presenting part, may be molded and edematous ( Fig. 42.5 ). Dunn noted that 32% of all deformations in the neonate were related to breech presentation. In his series of more than 6000 babies, 100% of genu recurvatum cases related to breech presentation, as did 50% of hip dislocation cases and 20% to 25% each for cases of mandibular asymmetry, torticollis, and talipes equinovarus ( Fig. 42.6 ). Traction to the brachial plexus or phrenic nerve during difficult deliveries or vaginal breech deliveries may occur, and 75% of cases of diaphragmatic paralysis caused by birth injury have associated brachial plexus palsy.

Craniofacial

The head is elongated into a dolichocephalic form, often with a prominent occipital shelf. There may be redundant folds of skin in the posterior neck as a result of compression due to retroflexion of the head ( Fig. 42.7 ). The lambdoid sutures may appear to be overlapping because of the fetal head constraint. The lower auricle may be forced upward into the location where the shoulder has been, and the manubrial region of the mandible may have a “hollow” appearance. The shoulder compression is often asymmetric; hence there may be asymmetry of the mandible with an upward “tilt” on the more compressed side. Torticollis may occur secondary to asymmetric stretching or frank tearing of the sternocleidomastoid muscle, or due to clavicular fracture during a traumatic breech vaginal delivery, and 20% of torticollis cases occur in babies who were in breech presentation. A study of 224 term infants in breech presentation compared with 3107 term infants in vertex presentation revealed the following anomalies to be associated with breech presentation: frontal bossing, prominent occiput, upward-slanting palpebral fissures, low-set ears, torticollis, and congenital hip dislocation. Dolichocephaly was confirmed by caliper measurements on 100 term infants in breech presentation and compared with 100 term infants in vertex presentation. Third-trimester biparietal diameters were smaller than expected in the breech infants, and the birth cephalic index was less than 76%.