Near term, the fetus typically turns spontaneously to a cephalic presentation as the increasing bulk of the buttocks seeks the more spacious fundus. However, if the fetal buttocks or legs enter the pelvis before the head, the presentation is breech. This fetal lie is more common remote from term as each fetal pole is of similar bulk earlier in pregnancy (Fig. 28-1). That said, breech presentation persists at term in 3 to 4 percent of singleton deliveries. The annual rate of breech presentation at delivery in nearly 270,000 singleton newborns at Parkland Hospital has varied from only 3.3 to 3.9 percent during the past 30 years.
Prevalence of breech presentation by gestational age at delivery in 58,842 singleton pregnancies at the University of Alabama at Birmingham Hospitals 1991 to 2006. (Data courtesy of Dr. John Hauth and Ms. Sue Cliver.)
Current obstetrical thinking regarding vaginal delivery of the breech fetus has been tremendously influenced by results reported from the Term Breech Trial Collaborative Group (Hannah, 2000). This trial included 1041 women randomly assigned to planned cesarean and 1042 to planned vaginal delivery. In the planned vaginal delivery group, 57 percent were actually delivered vaginally. Planned cesarean delivery was associated with a lower risk of perinatal mortality compared with planned vaginal delivery—3 per 1000 versus 13 per 1000. Cesarean delivery was also associated with a lower risk of “serious” neonatal morbidity—1.4 versus 3.8 percent.
The reaction to these findings by the American College of Obstetricians and Gynecologists (2001) resulted in an abrupt decline in the rate of attempted vaginal breech deliveries. Since those times, however, a more moderate plan was reached for management of breech delivery.
Critics of the Term Breech Trial emphasized that most of the outcomes included in the “serious” neonatal morbidity composite did not actually portend long-term disability. Moreover, as data from countries with low perinatal mortality rates became available, they showed infrequent perinatal deaths, and rates did not differ significantly between mode-of-delivery groups. Also, only nulliparas were included in the Term Breech Trial, and fewer than 10 percent underwent radiological pelvimetry. And last, the 2-year outcomes for children born during the original multicenter trial showed that planned cesarean delivery was not associated with a reduction in the rate of death or developmental delay (Whyte, 2004). Some of the large studies reporting the safety and risks of vaginal delivery for the term breech singleton are discussed further on Delivery Complications.
These findings prompted the American College of Obstetricians and Gynecologists (2012b) to modify its stance on breech presentation, and it currently recommends that “the decision regarding the mode of delivery should depend on the experience of the health care provider” and that “planned vaginal delivery of a term singleton breech fetus may be reasonable ...