Time of Birth and the Risk of Severe Unexpected Complications in Term Singleton Neonates.

Objective: To assess whether there is a relationship between evening, night, and weekend births and severe unexpected neonatal morbidity in low-risk term singleton births.

Methods: We conducted a population-based, cross-sectional analysis. Severe unexpected neonatal morbidity as defined by the National Quality Forum specification 0716 was derived from linked birth certificate and hospital discharge summaries for 1,048,957 low-risk singleton term Californian births during 2011 through 2013. The association between the nursing shift (7 am-3 pm vs 3-11 pm and 11 pm -7 am) and weekday compared with weekend birth and the risk of severe unexpected neonatal morbidity was estimated using mixed effects logistic regression models.

Results: Severe unexpected neonatal morbidity was higher among births during the 3-11 pm evening shift (2.1%) and the 11 pm-7 am night shift (2.1%), compared with those during the 7 am-3 pm day shift (1.8%). The adjusted odds ratios (ORs) were 1.10 (95% CI 1.06-1.13) for the evening shift and 1.15 (1.11-1.19) for the night shift. The adjusted ORs of severe unexpected neonatal morbidity were increased only on Sunday, as compared with other days (adjusted OR 1.08, 95% CI 1.02-1.14). When our analysis was by perinatal region, the increase was seen in four of the nine perinatal regions.

Conclusion: After risk adjustment, the risk of severe unexpected morbidity in the low-risk singleton California birth cohort was significantly increased on Sundays and births during evening and night shifts. These elevations were detected in only four of California's nine perinatal regions. Further analysis at the individual hospital level is warranted.