For preterm fetuses in younger subgroups-23 to 28 weeksthe data are more conflicting, and some studies describe no improved survival rate with planned cesarean delivery (Bergenhenegouwen, 2015; Kayem, 2015; Thomas, 2016). Forperiviable etuses, deined by them as 20 to 256/7 weeks, a consensus workshop of perinatal organizations concluded that "available data do not consistently support routine cesarean delivery to improve perinatal mortality or neurological outcomes for early preterm infants" (Raju, 2014). A subsequent joint statement by the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine (2017) suggested consideration for cesarean delivery for periviable fetuses beginning at 23°/7 weeks, with a recommendation for cesarean delivery at 25°1 weeks.
For more mature preterm breech fetuses, that is, between 32 and 37 weeks, again there are sparse data to guide delivery route selection. Bergenhenegouwen and coworkers (2015) studied more than 6800 breech deliveries in a subgroup between 32 and 37 weeks. With planned cesarean delivery, they found similar perinatal mortality rates but less composite mortality and severe morbidity. It appears in this subgroup that fetal weight rather than gestational age is likely more important. he Maternl-Fetal Nfedicine Committee of the Society of Obstetricians and Gynaecologists of Canada (SOGC) states that vaginal breech delivery is reasonable when the estimated fetal weight is >2500 g (Kotaska, 2009). There are especial concerns for delivery of the second noncephalic-presenting twin fetus that are discussed in Chapter 45 (p. 888).
In the United States, all these findings shape practice, and cesarean delivery is almost uniformly favored for the preterm breech fetus for which resuscitation is planned.
Increased rates of maternal and perinatal morbidity can be anticipated with breech presentations. For the mother, with either cesarean or vaginal delivery, genital tract laceration can be problematic. With cesarean delivery, added stretching of the lower uterine segment by forceps or by a poorly molded fetal head can extend hysterotomy incisions. With vaginal delivery, especially with a thinned lower uterine segment, delivery of the atercoming head through an incompletely dilated cervix or application of forceps may cause vaginal wall or cervical lacerations, and even uterine rupture. Manipulations may also extend an episiotomy, create deep perineal tears, and increase infection risks. Anesthesia suicient to induce appreciable uterine relaxation during vaginal delivery may cause uterine atony and in turn postpartum hemorrhage. Maternal death is rare, but rates appear higher in those with planned cesarean delivery for breech presentation-a case fatality rate of 0.47 maternal deaths per 1000 births (Schutte, 2007). Last, the risks associated with vaginal breech delivery are balanced against general cesarean delivery risks described in Chapter 30 (p. 568). Long-term, cesarean risks include those associated with repeated hysterotomy or with vaginal birth ater cesarean-VBAC-further described in Chapter 31 (p. 593).