Identifying appropriate pre-pregnancy body mass index classification to improve pregnancy outcomes in women of childbearing age in Beijing, China: a retrospective cohort study.

Background And Objectives: This study explored the appropriate classification of pre-pregnancy body mass index (BMI) in women of childbearing age in Beijing, China.

Methods And Study Design: Women with singleton pregnancies at more than 28 gestational weeks were retrospectively reviewed. Based on the pre-pregnancy BMI (kg/m2), these patients were divided into 7 groups: <18.5, >=18.5-22.9, >=23-23.9, >=24-24.9, >=25-27.9, >=28-29.9, and >=30. Pregnancy adverse outcomes, including gestational hypertension with or without preeclampsia, gestational diabetes mellitus, initial cesarean section, postpartum hemorrhage, macrosomia, large-for-gestational age infant and so on were recorded. Binary logistic regression analysis was used to calculate the uncorrected and corrected odds ratios and 95% confidence intervals, with the >=18.5-22.9 group serving as a reference.

Results: A total of 11,136 pregnant women were analyzed. Incidences of above mentioned six adverse outcomes were greater in women with higher pre-pregnancy BMI. The risks of the abovementioned six adverse outcomes were increased significantly among the >=23-23.9, >=24-24.9, >=25-27.9 groups and substantially higher in the >=28-29.9, >=30 groups after correction. <18.5 group showed an increased risk of small-for-gestational age infants.

Conclusions: For women of childbearing age in Beijing, China, the optimal pre-pregnancy BMI range was >=18.5-22.9 kg/m2, with the cutoff value for overweight status being >=23.0 kg/m2 and the cutoff value for obesity being >=28.0 kg/m2.