Association between weight gain during the first half of pregnancy and the risk of hypertension disorder of pregnancy: a prospective cohort study

Abstract

Objective: To explore the association between weight gain during the first half of pregnancy and the risk of hypertension disorder of pregnancy (HDP). Methods: This prospective cohort study recruited singleton pregnant women in the first trimester from November 2016 to March 2019 at 19 community hospitals in Tianjin. According to pre-pregnancy body mass index (BMI), the cohort was divided into 3 groups: underweight(BMI<18.5 kg/m2), normal-weight(18.5-24.9 kg/m2), and overweight/obese(≥25.0 kg/m2). The basic information of the participants was gathered through questionnaires, and the height, weight, and blood pressure of the participants were measured along with routine pregnancy examinations. The rate of gestational weight gain (rGWG) in the 3 periods (0-13+6, 14+0-20+6, and 0-20+6 weeks) of the participants was calculated. To observe the occurrence of HDP, the participants were followed up to 42 days postpartum. Using a generalized linear model, the association between rGWG at the 3 periods during the first half of pregnancy and HDP after 20 weeks of gestation was evaluated. Results: A total of 9 805 pregnant women were finally included, with the age of (30.6±3.8) years old, 9 418 (96.1%) Han ethnicity, and 6 845 (69.8%) primipara. There were 1 184 (12.1%), 6 831 (69.7%) and 1 790 (18.3%) participants in the underweight, normal-weight, and overweight/obese groups. Five hundreds and eight pregnant women were diagnosed with HDP (5.2%). The incidences of HDP were 1.8% (21/1 184), 3.9% (269/6 831), and 12.2% (218/1 790), respectively, in underweight, normal-weight, and overweight/obese groups. Adjusted for age, pre-pregnancy BMI, primipara, and family history of hypertension, women in the entire cohort with rGWG ≥ 0.18 kg/week before 13+6 weeks of pregnancy had a 28% higher HDP risk than those with rGWG ≤ 0.00 kg/week (RR=1.28, 95%CI 1.04-1.55, P=0.015), and the risk of HDP was increased by 39% in the overweight/obese group (RR=1.39, 95%CI 1.04-1.85, P=0.026), while no correlation was found between rGWG and HDP in underweight and normal-weight pregnant women (P>0.05). Weight gain during 14+0-20+6 weeks of pregnancy in any group was not related to the risk of HDP (P>0.05).In the entire cohort, compared to rGWG ≤0.14 kg/week, rGWG≥0.28 kg/week prior to 20+6 weeks increased HDP risk by 36% (RR=1.36, 95%CI 1.11-1.67, P=0.003). Normal-weight pregnant women with rGWG≥0.29 kg/week faced a 46% higher risk of HDP than those with rGWG≤0.15 kg/week (RR=1.46, 95%CI 1.11-1.93, P=0.008).In the overweight/obese group, excessive weight gain before 20+6 weeks seemed to increased risk of HDP, but the difference was not statistically significant (RR=1.35,95%CI 0.99-1.85, P=0.059), while the connection was nonexistent in underweight women. Conclusions: Except for pre-pregnancy underweight women, excessive weight gain during the first half of pregnancy is associated with increased risk of HDP among pregnant women.