title: Variation in hospital caesarean section rates for preterm births.
abstract: BACKGROUND
  Evidence about optimal mode of delivery for preterm birth is lacking, and there is thought to be considerable variation in practice.
  
  
  OBJECTIVE
  To assess whether variation in hospital preterm caesarean section rates (Robson Classification Group 10) and outcomes are explained by casemix, labour or hospital characteristics.
  
  
  METHODS
  Population-based cohort study in NSW, 2007-2011. Births were categorised according to degree of prematurity and hospital service capability: 26-31, 32-33 and 34-36 weeks' gestation. Hospital preterm caesarean rates were investigated using multilevel logistic regression models, progressively adjusting for casemix, labour and hospital factors. The association between hospital caesarean rates, and severe maternal and neonatal morbidity rates was assessed.
  
  
  RESULTS
  At 26-31 weeks' gestation, the caesarean rate was 55.2% (seven hospitals, range 43.4-58.4%); 50.9% at 32-33 weeks (12 hospitals, 43.4-58.1%); and 36.4% at 34-36 weeks (51 hospitals, 17.4-48.3%). At 26-31 weeks and 32-33 weeks' gestation, 81% and 59% of the variation between hospitals was explained with no hospital significantly different from the state average after adjustment. At 34-36 weeks' gestation, although 59% of the variation was explained, substantial unexplained variation persisted. Hospital caesarean rates were not associated with severe maternal morbidity rates at any gestational age. At 26-31 weeks' gestation, medium and high caesarean rates were associated with higher severe neonatal morbidity rates, but there was no evidence of this association ≥32 weeks.
  
  
  CONCLUSIONS
  Both casemix and practice differences contributed to the variation in hospital caesarean rates. Low preterm caesarean rates were not associated with worse outcomes.
authors.affiliation: Clinical and Population Perinatal Health Research, Kolling Institute, University of Sydney, St Leonards, NSW, Australia.
authors.forename: Melanie
authors.initials: M
authors.lastname: Bannister-Tyrrell
authors.affiliation: Clinical and Population Perinatal Health Research, Kolling Institute, University of Sydney, St Leonards, NSW, Australia.
authors.forename: Jillian A
authors.initials: JA
authors.lastname: Patterson
authors.affiliation: Clinical and Population Perinatal Health Research, Kolling Institute, University of Sydney, St Leonards, NSW, Australia.
authors.forename: Jane B
authors.initials: JB
authors.lastname: Ford
authors.affiliation: Kolling Institute, University of Sydney, St Leonards, NSW, Australia.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Morris
authors.affiliation: Department of Obstetrics and Gynaecology, Royal North Shore Hospital, St Leonards, NSW, Australia.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Nicholl
authors.affiliation: Clinical and Population Perinatal Health Research, Kolling Institute, University of Sydney, St Leonards, NSW, Australia.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Roberts
mesh_terms: D000293:Adolescent; D000328:Adult; D002585:Cesarean Section / Q000706:statistics & numerical data*; D002648:Child; D005260:Female; D005865:Gestational Age; D054625:Healthcare Disparities / Q000706:statistics & numerical data*; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D009517:New South Wales; D017063:Outcome Assessment, Health Care; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data*; D011247:Pregnancy; D047928:Premature Birth / Q000601:surgery*; D055815:Young Adult
keywords: caesarean section; maternal outcome; neonatal outcome; preterm birth; record linkage