Nighttime delivery and risk of neonatal encephalopathy

OBJECTIVE: The objective of the study was to determine the relationship between nighttime delivery and neonatal encephalopathy (NE). STUDY DESIGN: The design of the study was a retrospective population-based cohort of 1,864,766 newborns at a gestation of 36 weeks or longer in California, 1999-2002. We determined the risk of NE associated with nighttime delivery (7:00 pm to 6:59 am). RESULTS: Two thousand one hundred thirty-one patients had NE (incidence 1.1 per 1000 births). Nighttime delivery was associated with increased NE (odds ratio [OR], 1.13; 95% confidence interval [CI], 1.031.20), birth asphyxia (OR, 1.18; 95% CI, 1.081.29), and neonatal seizures (OR, 1.17; 95% CI, 1.071.28). In adjusted analyses, nighttime delivery was an independent risk factor for NE (OR, 1.10; 95% CI, 1.011.21), as were severe intrauterine growth retardation (OR, 3.8; 95% CI, 3.14.8); no prenatal care (OR, 2.0; 95% CI, 1.42.9); primiparity (OR, 1.5; 95% CI, 1.41.7); advanced maternal age (OR, 1.3; 95% CI, 1.161.45); and infant male sex (OR, 1.3; 95% CI, 1.21.4). CONCLUSION: Future studies of time of delivery may generate new strategies to reduce the burden of NE.