Association of prepregnancy body mass index and gestational weight gain trajectory with adverse pregnancy outcomes—a prospective cohort study in Shanghai

Objectives The objective was to investigate the associations of maternal prepregnancy body mass index (BMI) and gestational weight gain (GWG) trajectories with adverse pregnancy outcomes (APOs). Design This was a prospective cohort study. Setting This study was conducted in Shanghai Pudong New Area Health Care Hospital for Women and Children, Shanghai, China. Primary and secondary outcome measures A cohort study involving a total of 2174 pregnant women was conducted. Each participant was followed to record weekly weight gain and pregnancy outcomes. The Institute of Medicine classification was used to categorise prepregnancy BMI, and four GWG trajectories were identified using a latent class growth model. Results The adjusted ORs for the risks of large for gestational age (LGA), macrosomia, gestational diabetes mellitus (GDM) and hypertensive disorders of pregnancy (HDP) were significantly greater for women with prepregnancy overweight/obesity (OR=1.77, 2.13, 1.95 and 4.24; 95% CI 1.3 to 2.42, 1.32 to 3.46, 1.43 to 2.66 and 2.01 to 8.93, respectively) and lower for those who were underweight than for those with normal weight (excluding HDP) (OR=0.35, 0.27 and 0.59; 95% CI 0.22 to 0.53, 0.11 to 0.66 and 0.36 to 0.89, respectively). The risk of small for gestational age (SGA) and low birth weight (LBW) was significantly increased in the underweight group (OR=3.11, 2.20; 95% CI 1.63 to 5.92, 1.10 to 4.41; respectively) compared with the normal-weight group; however, the risk did not decrease in the overweight/obese group (p=0.942, 0.697, respectively). GWG was divided into four trajectories, accounting for 16.6%, 41.4%, 31.7% and 10.3% of the participants, respectively. After adjustment for confounding factors, the risk of LGA was 1.54 times greater for women in the slow GWG trajectory group than for those in the extremely slow GWG trajectory group (95% CI 1.07 to 2.21); the risk of SGA and LBW was 0.37 times and 0.46 times lower for women in the moderate GWG trajectory group and 0.14 times and 0.15 times lower for women in the rapid GWG trajectory group, respectively; the risk of macrosomia and LGA was 2.65 times and 2.70 times greater for women in the moderate GWG trajectory group and 3.53 times and 4.36 times greater for women in the rapid GWG trajectory group, respectively; and the women in the other three trajectory groups had a lower risk of GDM than did those in the extremely slow GWG trajectory group, but there was not much variation in the ORs. Notably, different GWG trajectories did not affect the risk of HDP. Conclusions As independent risk factors, excessively high and low prepregnancy BMI and GWG can increase the risk of APOs.