title: Trends in mode of delivery during 1984-2003: can they be explained by pregnancy and delivery complications?
abstract: OBJECTIVE
  To describe trends in mode of delivery, to identify significant factors which affected mode of delivery, and to describe how these factors and their impact have changed over time.
  
  
  METHODS
  Total population birth cohort.
  
  
  METHODS
  Western Australia 1984-2003.
  
  
  METHODS
  The analysis was restricted to all singleton infants delivered at 37-42 weeks of gestation with a cephalic presentation (n = 432,327).
  
  
  METHODS
  Logistic regression analyses were undertaken to estimate significant independent risk factors separately for elective and emergency caesarean sections compared with vaginal delivery (spontaneous and instrumental), adjusting for potential confounding variables.
  
  
  METHODS
  Trends in mode of delivery, demographic factors, and pregnancy and delivery complications. Estimated likelihood of elective caesarean section compared with vaginal delivery and emergency caesarean section compared with vaginal delivery.
  
  
  RESULTS
  Between 1984-88 and 1999-2003, the likelihood of women having an elective caesarean section increased by a factor of 2.35 times (95% CI 2.28-2.42) and the likelihood of an emergency caesarean section increased 1.89 times (95% CI 1.83-1.96). These caesarean section rate increases remained even after adjustment for their strong associations with many sociodemographic factors, obstetric risk factors, and obstetric complications. Rates of caesarean section were higher in older mothers, especially those older than 40 years of age (elective caesarean section, OR 5.42 [95% CI 4.88-6.01]; emergency caesarean section, OR 2.67 [95% CI 2.39-2.97]), and in nulliparous women (elective caesarean section, OR 1.54 [95% CI 1.47-1.61]; emergency caesarean section, OR 3.61 [95% CI 3.47-3.76]).
  
  
  CONCLUSIONS
  Our data show significant changes in mode of delivery in Western Australia from 1984-2003, with an increasing trend in both elective and emergency caesarean section rates that do not appear to be explained by increased risk or indication.
authors.affiliation: Telethon Institute for Child Health Research, Centre for Child Health Research, The University of Western Australia, West Perth, Western Australia, Australia. colleeno@ichr.uwa.edu.au
authors.forename: C M
authors.initials: CM
authors.lastname: O'Leary
authors.forename: N
authors.initials: N
authors.lastname: de Klerk
authors.forename: J
authors.initials: J
authors.lastname: Keogh
authors.forename: C
authors.initials: C
authors.lastname: Pennell
authors.forename: J
authors.initials: J
authors.lastname: de Groot
authors.forename: L
authors.initials: L
authors.lastname: York
authors.forename: S
authors.initials: S
authors.lastname: Mulroy
authors.forename: F J
authors.initials: FJ
authors.lastname: Stanley
mesh_terms: D000328:Adult; D015331:Cohort Studies; D036861:Delivery, Obstetric / Q000639:trends*; D005260:Female; D006801:Humans; D008423:Maternal Age; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology* / Q000628:therapy; D012044:Regression Analysis; D014904:Western Australia / Q000453:epidemiology