To determine whether delivery time of day is associated with differences in neonatal management or outcome in late preterm infants. Previous investigations of neonatal morbidity based on delivery time of day have focused on infants at term and early preterm gestational ages. This is a secondary analysis of ALPS, a multicenter trial of patients with anticipated late preterm delivery (34w0d-36w6d) randomized to betamethasone or placebo. Patients were assigned to a daytime (0700-1859) or nighttime cohort (1900-0659) using the documented time of birth. Study group characteristics were compared using chi-squared test for categorical data and Wilcoxon test for continuous data. Logistic regression models were used to adjust for birth weight, mode of delivery, and ALPS group assignment. The primary outcome was the administration of respiratory resuscitation in the first 30 minutes of life. Characteristics of the two cohorts are summarized in Table 1. There were 1539 daytime deliveries and 1288 nighttime deliveries. The daytime birth cohort had a significantly higher rate of Cesarean delivery and a higher mean birth weight. There was no significant difference in the primary outcome of administration of respiratory resuscitation in the first 30 minutes of life (aRR 1.03, 95% CI 0.86-1.24, p=0.73). Secondary outcomes, including administration of surfactant and NICU admission, were also comparable between the groups (Table 2). Of infants who received surfactant, the average duration of time to surfactant administration was not significantly different between daytime versus nighttime births. Previous studies have inconsistently demonstrated an association of delivery time of day with neonatal morbidity and mortality in early preterm and term infants. Here, we show that in late preterm infants, daytime compared to nighttime birth is not associated with increased neonatal morbidity.View Large Image Figure ViewerDownload Hi-res image Download (PPT)