Supplementary Material for: Time of delivery contributes to mortality and morbidity in preterm infants

Abstract Introduction Knowledge about the time of birth and its impact on premature infants is essential when planning perinatal and neonatal care and resource allocation. We studied the time of birth and its contribution to early death and morbidity in preterm infants. Methods We explored the time and mode of birth of infants with birthweight of <1500g and gestational age of <32+0/7 weeks. Additionally, we divided the infants into three groups stratified by their time of birth, i.e. during office hours, evening, and nighttime and assessed associations between these groups and mortality and morbidity. Results The study comprised 1610 infants of whom 156 (10%) died during their stay in NICU. The highest number of deliveries occurred on Fridays (21%, n=341/1610), primarily due to high number of cesarean sections. Deliveries peaked on workdays at 10 a.m. and 2 p.m. Mortality was lowest among infants born on Fridays (6%, n=21/341) and highest on Mondays (13%, n=28/218). Intraventricular hemorrhage (IVH) (OR 1.50, 95% Cl 1.10-2.03, p=0.010) and necrotizing enterocolitis (NEC) (OR 2.11, 95%Cl 1.13-3.91, p=0.019) were more common among infants born at nighttime. These associations attenuated after adjustment for covariates. Conclusion Deliveries of premature infants peaked on Fridays. Mortality was lower among those born on Fridays, compared with Mondays. Many low-risk deliveries on Fridays may decrease, and the tendency to postpone high-risk deliveries to Mondays, increase the proportional risk of mortality. Indication of higher risk of IVH and NEC among infants born during nighttime may be due to different patient population.