title: Effect of pre-pregnancy body mass index on adverse pregnancy outcome in north of China.
abstract: OBJECTIVE
  To investigate the effect of pre-pregnancy BMI on adverse maternal and neonatal outcomes in pregnancy women of northern China.
  
  
  METHODS
  We conducted a retrospective population-based cohort study of 5,047 singleton nulliparous pregnancies. The subjects were categorized into four groups by BMI-underweight (BMI < 18.5 kg/m(2)), normal (BMI 18.5-24 kg/m(2)), overweight (BMI 24-28 kg/m(2)) and obese (BMI ≥ 28 kg/m(2)). Logistic regression was used to adjust the potential confounder. Maternal and neonatal outcomes were evaluated with relative risks and 95% confidence intervals.
  
  
  RESULTS
  11.5, 63.4, 18.3, and 6.8% of the subjects were underweight, normal BMI, overweight and obese, respectively. Compared with women of normal BMI, the risk of the following outcomes was significantly increased in overweight and obese women and expressed as [adjusted RR (95% confidence interval)] respectively: pre-eclampsia [2.99 (2.21-4.06), 5.68 (3.97-8.11)]; gestational diabetes [2.49 (1.82-3.39), 4.35 (3.00-6.31)]; premature rupture of the membranes [1.64 (1.20-2.23), 1.73 (1.11-2.72)]; abruption placentae [1.84 (1.19-2.87), 2.79 (1.60-4.83)]; cesarian section [1.47 (1.27-1.70), 2.51 (1.97-3.20)]; postpartum hemorrhage [2.31 (1.51-3.54), 3.73 (2.37-5.04)]; perineal rupture [2.89 (1.44-5.81), 3.36 (1.55-7.30)]; large-for-gestational age [1.46 (1.02-2.08), 1.91 (1.17-3.10)]. However, anemia (2.54, 1.15-5.63), small-for-gestational age (1.67, 1.07-2.61) were significantly more common in the underweight group.
  
  
  CONCLUSIONS
  The prevalence of overweight and obesity in women of northern China is much lower than in the Caucasian population or Chinese in Hong Kong. The increased maternal BMI is associated with many adverse pregnancy outcomes and its risk increases with the degree of obesity. Maternal underweight has a protective effect although increases the risk of having small-for-gestational age baby and anemia.
authors.affiliation: Department of Obsterics and Gynecology, Shengjing Hospital, China Medical University, Shenyang, China.
authors.forename: Xuemin
authors.initials: X
authors.lastname: Liu
authors.forename: Juan
authors.initials: J
authors.lastname: Du
authors.forename: Guixi
authors.initials: G
authors.lastname: Wang
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Qi
authors.initials: Q
authors.lastname: Xi
mesh_terms: D000328:Adult; D015992:Body Mass Index; D001835:Body Weight; D002681:China / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D009765:Obesity / Q000453:epidemiology*; D050177:Overweight / Q000453:epidemiology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D011256:Pregnancy Outcome / Q000453:epidemiology*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013851:Thinness / Q000453:epidemiology*