Birth during off-hours: Impact of time of birth, staff´s seniority, and unit volume on maternal adverse outcomes-a population-based cross-sectional study of 87 065 deliveries.

Procedures performed during the night shift were not associated with increased complication rates. Delivery volume and high-volume centers were associated with the highest risk of maternal complications, and units with 500-1000 deliveries per year were the lowest. With increasing odds of pregnancy risks, these results change, and delivering in a high-volume center becomes at least as safe as delivering in a smaller unit.