Trends in maternal obesity and associated risks of adverse pregnancy outcomes in a population of Chinese women

Objective To assess the effect of increasing body mass index (BMI) on pregnancy outcome in a population of Chinese women. Design A retrospective study. Setting A university teaching hospital. Population Women delivering singleton babies between 1995 and 2005 who sought antenatal care before 20 weeks of gestation. Methods A total of 29 303 women were categorised into six BMI groups according to WHO's classification. Univariate, multivariate and logistic regression analysis were performed to compare obstetric and perinatal outcomes between BMI groups. Main outcome measures Incidences of caesarean delivery, pre-eclampsia, gestational diabetes, preterm delivery, small for gestational age (SGA) and large for gestational age (LGA), perinatal death, and the respective odd ratios in reference to the normal group with BMI >= 18.5 kg/m(2) and < 23 kg/m(2). Results The median BMI increased with increasing maternal age, parity, gestation at the first visit, but decreased with year of delivery (P < 0.001). Concerning the obstetric outcomes, increasing BMI was associated with increasing incidence of caesarean section, pre-eclampsia, gestational diabetes, preterm delivery, LGA, as well as SGA according to customised growth standards (P < 0.001). The odds ratios for most of these adverse outcomes are higher than those reported in Caucasian population. Increasing BMI was not associated with the rate of stillbirth, neonatal death or shoulder dystocia. Conclusions Increasing BMI is associated with increased risks of adverse obstetric outcomes. The impacts of high BMI on pre-eclampsia, gestational diabetes and preterm delivery in Chinese women might be stronger than that in Caucasian. Hence, it may be appropriate to use a lower BMI cutoff for defining overweight in Chinese.