Association among pre-pregnancy body mass index, gestational weight gain and neonatal birth weight: a prospective cohort study in China

BACKGROUND: This study aims to explore the relationships between pre-pregnancy body mass index (BMI), gestational weight gain (GWG), rate of GWG during the second and third trimesters (GWG(rate)) and birth weight among Chinese women. METHODS: Women were enrolled by 24 hospitals in 15 different provinces in mainland China from July 25th, 2017 to 26 November 2018. Pre-pregnancy BMI, GWG and GWG(rate) were calculated and divided in to different groups. The multinomial logistic regression model and restrictive cubic spline model were used to explore the relationships. RESULTS: Of the 3585 participants, women who were underweight, had insufficient GWG or GWG(rate) had 1.853-, 1850- or 1.524-fold higher risks for delivering small-for-gestational-age (SGA) infant compared with women who had normal BMI, sufficient GWG or GWG(rate). Women who were overweight/obese, had excessive GWG or GWG(rate) had 1.996-, 1676- or 1.673-fold higher risks for delivering large-for-gestational-age (LGA) infant. The effects of GWG and GWG(rate) on birth weight varied by pre-pregnancy BMI statuses. Dose-response analysis demonstrated L-shaped and S-shaped relationships between pre-pregnancy BMI, GWG, GWG(rate) and neonatal birth weight. CONCLUSIONS: Pre-pregnancy BMI, GWG or GWG(rate) were associated with neonatal birth weight among Chinese women. Both body weight before and during pregnancy should be maintained within the recommendations to prevent abnormal birth weight.