Objective: To determine whether delivery in the evening or at night and some organisational features of maternity units are related to perinatal adverse outcome.
Design: A 7-year national registry-based cohort study.
Setting: All 99 Dutch hospitals.
Population: From nontertiary hospitals (n = 88), 655 961 singleton deliveries from 32 gestational weeks onwards, and, from tertiary centres (n = 10), 108 445 singleton deliveries from 22 gestational weeks onwards.
Methods: Multiple logistic regression analysis of national perinatal registration data over the period 2000-2006. In addition, multilevel analysis was applied to investigate whether the effects of time of delivery and other variables systematically vary across different hospitals.
Main outcome measures: Delivery-related perinatal mortality (intrapartum or early neonatal mortality) and combined delivery-related perinatal adverse outcome (any of the following: intrapartum or early neonatal mortality, 5-minute Apgar score below 7, or admission to neonatal intensive care).
Results: After case mix adjustment, relative to daytime, increased perinatal mortality was found in nontertiary hospitals during the evening (OR, 1.32; 95% CI, 1.15-1.52) and at night (OR, 1.47; 95% CI, 1.28-1.69) and, in tertiary centres, at night only (OR, 1.20; 95% CI, 1.06-1.37). Similar significant effects were observed using the combined perinatal adverse outcome measure. Multilevel analysis was unsuccessful; extending the initial analysis with nominal hospital effects and hospital-delivery time interaction effects confirmed the significant effect of night in nontertiary hospitals, whereas other organisational effects (nontertiary, tertiary) were taken up by the hospital terms.
Conclusion: Hospital deliveries at night are associated with increased perinatal mortality and adverse perinatal outcome. The time of delivery and other organisational features representing experience (seniority of staff, volume) explain hospital-to-hospital variation.