Effect of birth timing on early morbidity and mortality in very preterm neonates: a single-center retrospective cohort study

BACKGROUND: Preterm birth is the leading cause of neonatal mortality and morbidity worldwide. Very preterm neonates born between 23 + 0 and 31 + 6 weeks of gestational age are at particularly high risk due to complications requiring immediate intervention. Whether the differential organization of healthcare services during working hours (full staffing) versus off-hours (on-call) affects neonatal outcomes remains debated. This study aims to evaluate the effect of in-hours versus off-hours birth timing on early morbidity and mortality in very preterm neonates. METHODS: This was a single-center, retrospective cohort study conducted in a tertiary neonatal intensive care unit between January 1, 2014 and December 31, 2021. A total of 326 very preterm neonates born between 23 + 0 and 31 + 6 weeks of gestational age were included. Neonates were divided into two groups according to birth timing: Group 1 (In-hours: 08:00-17:00 on weekdays) and Group 2 (Off-hours: 17:01-07:59 on weekdays, weekends, and public holidays). Demographic data and neonatal outcomes were compared between groups, and risk factors for mortality were examined using multivariate logistic regression analysis. RESULTS: No statistically significant difference was found between groups regarding gestational age, birth weight, or in-hospital mortality (Group 1: 25.3% vs. Group 2: 23.2%, p = 0.658). However, maternal risk factors such as gestational hypertension (p = 0.005) and placental insufficiency (p = 0.001) were significantly higher in the in-hours group. In multivariate analysis, low 5-minute Apgar scores and advanced-stage NEC (stage ≥ 3 A) were identified as independent risk factors for mortality in both groups. Advanced-stage NEC showed a high odds ratio in both cohorts, though accompanied by wide confidence intervals due to small event sizes. CONCLUSIONS: Birth timing (in-hours versus off-hours) had no significant effect on overall mortality or major morbidity in very preterm neonates, reflecting the continuity of care standards at our center. Advanced-stage NEC remained a critical predictor of mortality across both groups, independent of birth timing.