title: Does size matter? A population-based study of birth in lower volume maternity hospitals for low risk women.
abstract: OBJECTIVE
  To study the association between volume of hospital births per annum and birth outcome for low risk women.
  
  
  METHODS
  Population-based study using the National Perinatal Data Collection (NPDC).
  
  
  METHODS
  Australia.
  
  
  METHODS
  Of 750,491 women who gave birth during 1999-2001, there were 331,147 (47.14%) medically 'low risk' including 132,696 (40.07%) primiparae and 198,451 (59.93%) multiparae.
  
  
  METHODS
  The frequency of each birth and infant outcome was described according to the size of the hospital where birth took place. We investigated whether unit size (defined by volume) was an independent risk factor for each outcome factor using public hospitals with greater than 2000 births per annum as a reference point.
  
  
  METHODS
  Rates of intervention at birth and neonatal mortality for low risk women in relation to hospitals with <100, 100-500, 501-1000, 1001-2000 and >2001 births per annum.
  
  
  RESULTS
  Neonatal death was less likely in hospitals with less than 2000 births per annum regardless of parity. For multiparous low risk women in hospitals of 100 and 500 births per annum compared with hospitals of >2000 births per annum the adjusted odds of neonatal mortality [adjusted odds ratio (AOR) 0.36; 99% confidence interval (CI) 0.14-0.93]. For low risk primiparous women in hospitals with less than 100 births per annum, there were lower rates of induction of labour (AOR 0.62; 99% CI 0.54-0.73); intrathecal analgesia/anaesthesia (AOR 0.34; 99% CI 0.28-0.42); instrumental birth (AOR 0.80; 99% CI 0.69-0.93); caesarean section after labour (AOR 0.59; 99% CI 0.49-0.72) and admission to a neonatal unit (AOR 0.15; 99% CI 0.10-0.22) and for low risk multiparous women in hospitals with less than 100 births per annum: induction (AOR 0.69; 99% CI 0.62-0.76); intrathecal analgesia/anaesthesia (AOR 0.32; 99% CI 0.29-0.36); instrumental birth (AOR 0.52; 99% CI 0.41-0.67); caesarean section after labour (AOR 0.41; 99% CI 0.33-0.52); and admission to a neonatal unit (AOR 0.09; 99% CI 0.07-0.12).
  
  
  CONCLUSIONS
  In Australia, lower hospital volume is not associated with adverse outcomes for low risk women.
authors.affiliation: Australian Institute of Health and Welfare (AIHW), National Perinatal Statistics Unit, University of New South Wales, Sydney, Australia.
authors.forename: Sally K
authors.initials: SK
authors.lastname: Tracy
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Sullivan
authors.forename: Hannah
authors.initials: H
authors.lastname: Dahlen
authors.forename: Deborah
authors.initials: D
authors.lastname: Black
authors.forename: Yueping Alex
authors.initials: YA
authors.lastname: Wang
authors.forename: Mark B
authors.initials: MB
authors.lastname: Tracy
mesh_terms: D000328:Adult; D000368:Aged; D001315:Australia / Q000453:epidemiology; D001723:Birth Rate; D005260:Female; D006276:Health Facility Size / Q000592:standards; D006771:Hospitals, Maternity / Q000592:standards / Q000706:statistics & numerical data*; D006779:Hospitals, Public / Q000706:statistics & numerical data; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D015931:Intensive Care, Neonatal / Q000706:statistics & numerical data; D016017:Odds Ratio; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D012307:Risk Factors