title: Maternal obesity, caesarean delivery and caesarean delivery on maternal request: a cohort analysis from China.
abstract: BACKGROUND
  To quantify the association between maternal obesity and caesarean delivery, particularly caesarean delivery on maternal request (CDMR), a fast-growing component of caesarean delivery in many nations.
  
  
  METHODS
  We followed 1,019,576 nulliparous women registered in the Perinatal Healthcare Surveillance System during 1993-2010. Maternal body mass index (BMI, kg/m(2) ), before pregnancy or during early pregnancy, was classified as underweight (<18.5), normal (18.5 to <23; reference), overweight (23 to <27.5), or obese (≥27.5), consistent with World Health Organization guidelines for Asian people. The association between maternal obesity and overall caesarean and its subtypes was modelled using log-binomial regression.
  
  
  RESULTS
  During the 18-year period, 404,971 (39.7%) caesareans and 93,927 (9.2%) CDMRs were identified. Maternal obesity was positively associated with overall caesarean and CDMR. Adjusted risk ratios for overall caesarean in the four ascending BMI categories were 0.96 [95% confidence interval (CI) 0.94, 0.97], 1.00 (Reference), 1.16 [95% CI 1.14, 1.18], 1.39 [95% CI 1.43, 1.54], and for CDMR were 0.95 [95% CI 0.94, 0.96], 1.00 (Reference), 1.20 [95% CI 1.18, 1.22], 1.48 [95% CI 1.433, 1.54]. Positive associations were consistently found in women residing in southern and northern provinces and in subgroups stratified by year of delivery, urban or rural residence, maternal age, education, level of delivering hospital, and birthweight.
  
  
  CONCLUSIONS
  In a large Chinese cohort study, maternal obesity was associated with an increased risk of caesarean delivery and its subtypes, including CDMR. Given the rising global prevalence of obesity, and in view of the growth of CDMR, it seems likely that caesarean births will increase, unless there are changes in obstetrical practice.
authors.affiliation: Institute of Reproductive and Child Health, Ministry of Health Key Laboratory of Reproductive Health, Peking University Health Science Center, Beijing, China; Department of Epidemiology and Biostatistics, School of Public Health, Peking University Health Science Center, Beijing, China.
authors.forename: Yubo
authors.initials: Y
authors.lastname: Zhou
authors.forename: Jan
authors.initials: J
authors.lastname: Blustein
authors.forename: Hongtian
authors.initials: H
authors.lastname: Li
authors.forename: Rongwei
authors.initials: R
authors.lastname: Ye
authors.forename: Liping
authors.initials: L
authors.lastname: Zhu
authors.forename: Jianmeng
authors.initials: J
authors.lastname: Liu
mesh_terms: D000328:Adult; D044466:Asian People / Q000706:statistics & numerical data*; D015992:Body Mass Index; D002585:Cesarean Section / Q000706:statistics & numerical data; D002681:China / Q000453:epidemiology; D004522:Educational Status; D017558:Elective Surgical Procedures; D004630:Emergencies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008423:Maternal Age; D009035:Mothers; D009765:Obesity / Q000150:complications / Q000453:epidemiology*; D016017:Odds Ratio; D011247:Pregnancy; D015995:Prevalence; D012307:Risk Factors; D012923:Social Class; D014481:United States / Q000453:epidemiology
keywords: body mass index; caesarean delivery; caesarean delivery on maternal request; obesity