title: Caesarean section rates in Southwestern Ontario: changes over time after adjusting for important medical and social characteristics.
abstract: OBJECTIVE
  To compare Caesarean section rates in a cohort of women in Southwestern Ontario over time, overall, and in patient subgroups defined by the Robson criteria, after adjusting for important medical and social characteristics.
  
  
  METHODS
  We obtained data from a perinatal database on deliveries at ≥ 22 weeks' gestation at a level II centre and a level III centre in London, Ontario between 1999 and 2010. Caesarean section rates were examined overall and in subgroups defined by parity, presentation, plurality, gestational age, and history of previous Caesarean section. Multivariable modified Poisson regression was used to compare Caesarean section rates in 2003-2006 and 2007-2010 versus 1999-2002.
  
  
  RESULTS
  In the fully adjusted models, the overall Caesarean section rate was significantly higher in 2007-2010 than in 1999-2002 for the level II centre (adjusted relative risk [aRR] 1.12; 95% CI 1.05 to 1.21). An increase was also seen in the level III centre in both 2003 to 2006 (aRR 1.19; 95% CI 1.14 to 1.24) and 2007 to 2010 (aRR 1.17; 95% CI 1.12 to 1.22). Similar increases were seen over time among patient subgroups. Notably, repeat Caesarean sections without labour increased at the level II centre (2003 to 2006 aRR 1.21; 95% CI 1.01 to 1.45, and 2007 to 2010 aRR 1.44; 95% CI 1.21 to 1.71) and the level III centre (2003 to 2006 aRR 1.72; 95% CI 1.53 to 1.94, and 2007 to 2010 aRR 1.77; 95% CI 1.57 to 2.00).
  
  
  CONCLUSIONS
  There has been a significant increase over time in the Caesarean section rate overall and in important subgroups. This increase remains even after controlling for other factors which may explain the trend.
authors.affiliation: Department of Obstetrics and Gynaecology, The University of Western Ontario, London ON; Department of Epidemiology and Biostatistics, The University of Western Ontario, London ON.
authors.forename: Hilary K
authors.initials: HK
authors.lastname: Brown
authors.affiliation: Quality Measurement and Clinical Decision Support, St. Joseph's Health Care, London ON.
authors.forename: Jacquelyn
authors.initials: J
authors.lastname: Hill
authors.affiliation: Department of Obstetrics and Gynaecology, The University of Western Ontario, London ON.
authors.forename: Renato
authors.initials: R
authors.lastname: Natale
mesh_terms: D000328:Adult; D002585:Cesarean Section / Q000706:statistics & numerical data*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D009864:Ontario; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology / Q000601:surgery; D012189:Retrospective Studies; D012931:Social Environment; D013997:Time Factors; D055815:Young Adult
keywords: Caesarean section; obstetrics; primary Caesarean section; repeat Caesarean section