Associations Of Pre-pregnancy Body Mass Index And Rate Of Gestational Weight Gain With Adverse Pregnant Outcomes: A Prospective Birth Cohort Study In China

Objective: To evaluate associations of maternal pre-pregnancy body mass index(BMI) and rate of gestational weight gain(GWG) with adverse pregnancy outcomes in Wuhan, China, and provide a reference for the prevention of adverse pregnancy outcomes.Methods: In the prospective birth cohort study, pregnant women who visited the Wuhan Medical and Health Center for Women and Children during November 2012 and November 2014 were selected and tracked pregnancy outcomes. Data, such as living habits, nutritional status and so on, were collected by face-to-face or telephone-assistant questionnaires. Clinical records were used to track pregnancy outcomes and information about newborns. We used restricted cubic spline and binary logistic regression to explore relationships among pre-pregnancy BMI, rate of GWG and adverse pregnancy outcomes.Results:1. In total, 11020 women with complete data on maternal and fetal outcomes participated in the cohort. 23.39% of pregnant women were underweight, and 23.39%were overweight or obese. 10.66% of them had excessive rate of GWG, and 10.04%had inadequate rate of GWG. Women who gain weight lower or higher than the IOM guidelines were accounted for 58.07% and 8.71%, respectively. Pre-pregnancy BMI and rate of GWG had statistical differences among different age, culture level,occupation, family income, and parity in pregnant women(P<0.05).2. As restricted cubic spline shown, there was a “U” shaped dose-response relationship between rate of GWG and preterm. It indicated that both inadequate and excessive rate of GWG increased risks for preterm birth. In addition, with the increase of pre-pregnancy BMI and rate of GWG, the risk decreased for low birth weight,while increased for macrosomia and cesarean delivery.3. Results from logistic regression analysis showed that compared to women with normal weigh, underweight women were 1.53 times in risk to have preterm;overweight or obese women were 2.59 and 1.89 times in risk to have cesarean delivery and macrosomia, respectively. We also found inadequate rate of GWG were risk factors for preterm(OR=1.75) and low birth weight(OR=1.98). Excessive rate of GWG were risk factors for preterm birth(OR=1.45), cesarean delivery(OR=1.55) and macrosomia(OR=2.85). Compared to women who gain weight within the IOM guidelines, the odds ratio of preterm birth was 1.50 for women who gain weight lower than the guidelines. The odds ratios of cesarean delivery and macrosomia were 1.30 and 2.98 for women who gain weight higher than the guidelines.4. As stratification analysis shown, compared to women with normal weigh and rate of GWG, underweight women with inadequate rate of GWG had higher risks for preterm(OR=1.90) and low birth weight(OR=2.51). Overweight or obese women with excessive rate of GWG had higher risks for cesarean delivery and macrosomia,with OR as 2.45 and 4.26, respectively.Conclusion: Unreasonable pre-pregnancy BMI and rate of GWG were associated with increased risks for adverse pregnancy outcomes. We need to develop new GWG guidelines because IOM recommendation may not suitable for the Chinese women.Considering the joint association of pregnancy BMI and GWG, guidance during pregnancy should be conducted based on pre-pregnancy BMI and GWG.