title: Contribution of prepregnancy body mass index and gestational weight gain to caesarean birth in Canada.
abstract: BACKGROUND
  Overweight and obese women are known to be at increased risk of caesarean birth. This study estimates the contribution of prepregnancy body mass index (BMI) and gestational weight gain (GWG) to caesarean births in Canada.
  
  
  METHODS
  We analyzed data from women in the Canadian Maternity Experiences Survey who had a singleton term live birth in 2005-2006. Adjusted odds ratios for caesarean birth across BMI and GWG groups were derived, separately for nulliparous women and parous women with and without a prior caesarean. Population attributable fractions of caesarean births associated with above normal BMI and excess GWG were calculated.
  
  
  RESULTS
  The overall caesarean birth rate was 25.7%. Among nulliparous and parous women without a previous caesarean birth, rates in obese women were 45.1% and 9.7% respectively, and rates in women who gained above their recommended GWG were 33.5% and 8.0% respectively. Caesarean birth was more strongly associated with BMI than with GWG. However, due to the high prevalence of excess GWG (48.8%), the proportion of caesareans associated with above normal BMI and excess GWG was similar [10.1% (95% CI: 9.9-10.2) and 10.9% (95% CI: 10.7-11.1) respectively]. Overall, one in five (20.2%, 95% CI: 20.0-20.4) caesarean births was associated with above normal BMI or excess GWG.
  
  
  CONCLUSIONS
  Overweight and obese BMI and above recommended GWG are significantly associated with caesarean birth in singleton term pregnancies in Canada. Strategies to reduce caesarean births must include measures to prevent overweight and obese BMI prior to conception and promote recommended weight gain throughout pregnancy.
authors.affiliation: Maternal and Infant Health Section, Surveillance and Analysis Division, Public Health Agency of Canada, 785 Carling Avenue, 6804A 4th Floor, Ottawa, ON K1A 0K9, Canada. sdzakpasu@yahoo.ca.
authors.forename: Susie
authors.initials: S
authors.lastname: Dzakpasu
authors.forename: John
authors.initials: J
authors.lastname: Fahey
authors.forename: Russell S
authors.initials: RS
authors.lastname: Kirby
authors.forename: Suzanne C
authors.initials: SC
authors.lastname: Tough
authors.forename: Beverley
authors.initials: B
authors.lastname: Chalmers
authors.forename: Maureen I
authors.initials: MI
authors.lastname: Heaman
authors.forename: Sharon
authors.initials: S
authors.lastname: Bartholomew
authors.forename: Anne
authors.initials: A
authors.lastname: Biringer
authors.forename: Elizabeth K
authors.initials: EK
authors.lastname: Darling
authors.forename: Lily S
authors.initials: LS
authors.lastname: Lee
authors.forename: Sarah D
authors.initials: SD
authors.lastname: McDonald
mesh_terms: D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D002170:Canada / Q000453:epidemiology; D002585:Cesarean Section / Q000639:trends*; D003430:Cross-Sectional Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D009765:Obesity / Q000453:epidemiology*; D016017:Odds Ratio; D050177:Overweight / Q000453:epidemiology*; D010298:Parity; D011247:Pregnancy; D011256:Pregnancy Outcome; D011263:Pregnancy Trimester, Third; D015995:Prevalence; D011379:Prognosis; D012189:Retrospective Studies; D015430:Weight Gain / Q000502:physiology*; D055815:Young Adult