Does Time of Delivery Influence the Risk of Neonatal Morbidity?

Objective To examine whether time of delivery influences the risk of neonatal morbidity among women with singleton pregnancies. Study Design Secondary analysis of data from the Maternal Fetal Medicine Units Network Factor V Leiden Mutation study. We categorized time of delivery as day (07:00-16:59), evening (17:00-23:59), and overnight (midnight-06:59). Severe neonatal morbidity was defined by at least one of the following: respiratory distress syndrome, transient tachypnea of the newborn, sepsis, seizures, neonatal intensive care admission, or a 5-minute APGAR ≤3. We calculated frequencies of severe neonatal morbidity by time of delivery. Multivariate analysis was performed to determine whether time of delivery was independently associated with severe neonatal morbidity. Results Among 4,087 women, 1,917 (46.9%) delivered during the day, 1,140 (27.9%) delivered in the evening, and 1,030 (25.2%) delivered overnight. We observed no significant differences in the rates of neonatal morbidity between delivery time periods (day: 12.3%; evening: 12.8%; overnight: 12.6%; p = 0.9). No significant association was observed between time of delivery and neonatal morbidity after adjustment for maternal, obstetric, and peripartum factors. Conclusion Our findings suggest that time of delivery is not associated with severe neonatal morbidity.