Safety of vaginal delivery for preterm birth depends on fetal presentation

The Consortium on Safe Labor study looked at maternal and fetal data on 228,668 deliveries between 2002 and 2008, based on medical records for all singleton deliveries at ≥24 to <32 weeks' gestation from 4352 pregnancies. Precursors to delivery were classified as preterm labor, preterm premature rupture of membranes, or indicated delivery. In a subgroup of 2906 pregnancies, neonatal outcomes were assessed after attempted vaginal delivery versus planned cesarean delivery, subdivided by gestational age (24 to 27 versus 28 to 31 weeks).

Neonatal outcomes differed by fetal presentation. For vertex presentations at 24 to 27 weeks, vaginal delivery was attempted in 77% of cases and produced no significant differences in death rates compared with planned cesarean (mortality 15.2% versus 13.5%, respectively; P=0.581). Vaginal delivery therefore was successful in 85% of cases. Breech presentations, however, were less likely to be delivered vaginally (32%), and vaginal delivery was associated with a higher mortality rate (25.2% versus 13.2%; P=0.003). Breech pregnancies with planned cesarean delivery were more likely to be complicated by neonatal sepsis and need for ventilation (both P<0.05).

Multivariate analyses confirmed that vertex deliveries incurred no differences in neonatal mortality by delivery method at either gestational interval. Breech presentations, however, had an increased risk of mortality with attempted vaginal delivery both at 24 to 27 weeks (relative risk [RR] 3.0; 95% confidence interval [CI], 1.8-5.1) and 28 to 31 weeks (RR 5.1; 95% CI, 1.3-19.9).

When advising women at <32 weeks' gestation, practitioners should be aware that vaginal delivery is just as safe as cesarean delivery for vertex presentations, but planned cesarean reduces neonatal mortality for breech presentations.

Reddy UM, Zhang J, Sun L, Chen Z, Raju TN, Laughon SK. Neonatal mortality by attempted route of delivery in early preterm birth. Am J Obstet Gynecol. 2012;207(2):117.e1-e8.