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], 1.03-1.20), 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).
Conclusion: Future studies of time of delivery may generate new strategies to reduce the burden of NE.
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