title: The association between hospital obstetric volume and perinatal outcomes in California.
abstract: OBJECTIVE
  We sought to analyze the association between hospital obstetric volume and perinatal outcomes in California.
  
  
  METHODS
  This was a retrospective cohort study of births occurring in California in 2006. Hospitals were divided into 4 obstetric volume categories. Unadjusted rates of neonatal mortality and birth asphyxia were calculated for each category, overall and among term deliveries with birthweight >2500 g. Multivariable logistic regression was used to control for confounders. Deliveries in rural hospitals were analyzed separately using different volume categories.
  
  
  RESULTS
  Prevalence of asphyxia increased with decreasing hospital volume overall and among term, non-low-birthweight infants, from 9/10,000 live births at highest-volume hospitals to 18/10,000 live births at the lowest-volume hospitals (P < .001). Similar trends were observed in rural hospitals, with rates increasing from 7-34/10,000 live births in low-volume rural hospitals (P < .001).
  
  
  CONCLUSIONS
  These findings provide evidence for an inverse association between hospital obstetric volume and birth asphyxia.
authors.affiliation: Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, OR, USA.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Snowden
authors.forename: Yvonne W
authors.initials: YW
authors.lastname: Cheng
authors.forename: Caitlin P
authors.initials: CP
authors.lastname: Kontgis
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Caughey
mesh_terms: D001238:Asphyxia Neonatorum / Q000453:epidemiology*; D002140:California / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D006780:Hospitals, Rural / Q000706:statistics & numerical data; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D009775:Obstetrics and Gynecology Department, Hospital / Q000706:statistics & numerical data*; D011247:Pregnancy; D015995:Prevalence; D012189:Retrospective Studies; D047929:Term Birth