Nighttime delivery and risk of neonatal encephalopathy.

Abstract

The objective of the study was to determine the relationship between nighttime delivery and neonatal encephalopathy (NE). 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)). 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], 1.03-1.20), birth asphyxia (OR, 1.18; 95% CI, 1.08-1.29), and neonatal seizures (OR, 1.17; 95% CI, 1.07-1.28). In adjusted analyses, nighttime delivery was an independent risk factor for NE (OR, 1.10; 95% CI, 1.01-1.21), as were severe intrauterine growth retardation (OR, 3.8; 95% CI, 3.1-4.8); no prenatal care (OR, 2.0; 95% CI, 1.4-2.9); primiparity (OR, 1.5; 95% CI, 1.4-1.7); advanced maternal age (OR, 1.3; 95% CI, 1.16-1.45); and infant male sex (OR, 1.3; 95% CI, 1.2-1.4). Future studies of time of delivery may generate new strategies to reduce the burden of NE.