Supplementary Material for: Periconceptional Supplementation with Folic Acid or Multiple Micronutrients Containing Folic Acid and the Risk for Hypertensive Disorders in Pregnancy

Objective: The aim of this study was to investigate the association between supplementation containing folic acid only (FAO) or multiple micronutrients containing folic acid and the risk for hypertensive disorders in pregnancy (HDP). Subjects and Methods: The retrospective cohort study was based on data from women who gave birth from 2016 to 2018 at Tongzhou Maternal and Child Health Care Hospital of Beijing, China. The outcomes were HDP diagnosed after the 20th week of pregnancy, including gestational hypertension (GH), preeclampsia, and eclampsia. Associations between supplementation patterns and HDP were estimated by Poisson loglinear regression models. Sensitivity analyses were based on prepregnancy body mass index (BMI) and maternal age. Results: Among the 25,866 women included in the study, periconceptional use of FA supplementation marginally reduced the risk for HDP (adjusted risk ratio [aRR] = 0.87, 95% confidence interval [CI] 0.73–1.04). Women who began FAO supplementation before conception had a lower risk for GH compared to those who began after conception (aRR = 0.59, 95% CI: 0.45–0.78). The risk for HDP also reduced among FAO users who began supplementation before conception with a normal prepregnancy BMI (aRR = 0.64, 95% CI: 0.49–0.84) and users ≥30 years old (aRR = 0.75, 95% CI: 0.58–0.98). Conclusions: Periconceptional FAO supplementation may reduce the risk for HDP, especially GH. The protective effects are greater among women with a normal prepregnancy BMI and those ≥30 years old.