Associations Between Pre-Pregnancy Body Mass Index, Gestational Weight Gain and Preterm Birth: a Cohort Study in Wuhan, China

Background Preterm birth (PTB) is the leading cause of neonatal mortality and morbidity worldwide. Methods This cohort study was designed to investigate the associations between pre-pregnancy BMI, total gestational weight gain (GWG), and GWG during early pregnancy with PTB utilizing data of 83,096 Chinese women from the Maternal and Children Healthcare Information Tracking System of Wuhan, China. Results Women who were underweight, overweight or obese prior to pregnancy had an overall elevated risk of PTB, compared to their normal weight counterparts. Women with total GWG below the IOM recommendation had an increased risk of PTB compared to women who had GWG within the recommendation, whereas an increasing risk of PTB was observed asweekly early pregnancy GWGincreased. When stratified by subtypes of PTB, pre-pregnancy underweight was associated with higher risk of spontaneous PTB, and pre-pregnancy overweight /obese increased the risk of both spontaneous PTB and medically indicated PTB. Women with total GWG below the IOM recommendation had elevated risk for spontaneous PTB and PROM, and women with GWG above the recommendation had decreased risk for all three subtypes of PTB, whereas risk for the three subtypes of PTB increased along with increasing weekly GWG of early pregnancy. Conclusions Maternal underweight, overweight/obesity, total GWG, and GWG during early pregnancy should be considered in combination to reduce the risk of PTB, women should modify their weight gains during pregnancy according to the results.