title: Nighttime delivery and risk of neonatal encephalopathy.
abstract: OBJECTIVE
  The objective of the study was to determine the relationship between nighttime delivery and neonatal encephalopathy (NE).
  
  
  METHODS
  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).
  
  
  CONCLUSIONS
  Future studies of time of delivery may generate new strategies to reduce the burden of NE.
authors.affiliation: Department of Neurology, University of California School of Medicine, San Francisco, 94117, USA. wuy@neuropeds.ucsf.edu
authors.forename: Yvonne W
authors.initials: YW
authors.lastname: Wu
authors.forename: Trinh N
authors.initials: TN
authors.lastname: Pham
authors.forename: Beate
authors.initials: B
authors.lastname: Danielsen
authors.forename: Dena
authors.initials: D
authors.lastname: Towner
authors.forename: Lloyd
authors.initials: L
authors.lastname: Smith
authors.forename: S Claiborne
authors.initials: SC
authors.lastname: Johnston
mesh_terms: D001238:Asphyxia Neonatorum / Q000150:complications* / Q000453:epidemiology; D001927:Brain Diseases / Q000453:epidemiology / Q000209:etiology*; D002140:California / Q000453:epidemiology; D036861:Delivery, Obstetric / Q000009:adverse effects* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009551:Night Care / Q000706:statistics & numerical data; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors