For women with prior cesarean, optimal gestational age for elective delivery is week 39

"Prior studies have compared the perinatal risks of elective delivery at 37 to 41 weeks gestation, but didn't evaluate the hazard of delivery versus not delivering at a specific time point," said Giuseppe Chiossi, MD, who conducted the study for the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Maternal-Fetal Medicine Units Network, Bethesda, Md. "We wanted to compare the risks of elective repeat cesarean at each gestational age starting at 37 weeks with the cumulative maternal and neonatal risks of not delivering at that particular gestational age."

The study, entitled Timing of Delivery and Adverse Outcomes in Term Singleton Repeat Cesarean Deliveries (CD), found that elective repeat cesarean deliveries at a later gestational age were associated with significantly lower rates of composite adverse neonatal outcomes when compared with 37 and 38 weeks deliveries. Moreover, adverse neonatal outcomes were significantly more frequent in pregnancies continued beyond 39 weeks versus elective cesarean at 39 weeks. On the other hand, maternal outcomes tended to be better with continued pregnancy rather than elective cesarean at 37 or 38 weeks, but the difference was significant only at 37 weeks. Composite maternal outcomes were significantly worse for later deliveries compared with elective cesarean at 39 weeks. These associations remained after controlling for confounders.