The timing of elective caesarean deliveries and early neonatal outcomes in singleton infants born 37-41 weeks' gestation.

Background: Births by elective caesarean section (CS) are rising, particularly before 39 weeks' gestation, which may be associated with unacceptably high risk of adverse neonatal outcomes. The optimal timing of these deliveries needs to be determined with recent recommendations to delay births by elective CS until 39 weeks.

Aims: To evaluate the association between gestational age (GA) at delivery and neonatal outcomes after elective CS between 37 and 41 weeks.

Materials And Methods: Retrospective cohort study of viable singleton neonates delivered by elective CS at Mater Mothers' Hospitals (1998-2009). Neonates were stratified into two GA groups with early term (ET, 37-38 weeks) compared with the reference group of full and late term (FLT, 39-41 weeks). The primary outcome examined was serious respiratory morbidity; secondary outcomes included depression at birth, nursery admission and assisted ventilation.

Results: Fourteen thousand and four hundred and forty-seven mother-baby pairs were included (59.9% delivered before 39 weeks). There was a significantly decreasing risk of adverse neonatal outcomes with increasing GA. Compared to FLT, delivery at ET almost tripled the risk of the primary outcome (AOR 2.74; 95% CI 1.79-4.21). Rates of most secondary outcomes were at least doubled.

Conclusion: Elective CS performed at 37-38 weeks is associated with poorer neonatal outcomes compared to those delivered at 39-41 weeks. This study supports recent recommendations to delay delivery by elective CS until week 39 if possible.