RESUMEN
Objective: To investigate the relationship between folic acid supplementation and the risk of preeclampsia (PE). Methods: A total of 9 048 pregnant women were selected from the First Hospital of Shanxi Medical University in Taiyuan from March 2012 to September 2016. Among them, 882 pregnant women with PE were divided into case group, and 8 166 pregnant women without PE were divided into control group. Information on demographic characteristics, folic acid supplementation, maternal complications, and other factors were collected by face-to-face interviews after child birth in the hospital. Unconditional logistic regression analyses were used to investigate the relationship between folic acid supplementation and the risk of PE and the effects of pre-pregnancy BMI on the relationship of folic acid supplementation with the risk of PE. Results: Compared with nonusers, folic acid supplement users had reduced risk of PE (OR=0.79, 95%CI: 0.64-0.96). Folic acid supplementation before and during pregnancy were negatively related with the risk of PE (OR=0.63, 95%CI: 0.49-0.81). Pregnant women who used folic acid tablets only or used both folic acid tablets and multivitamin containing folic acid had reduced risk of PE (OR=0.81, 95%CI: 0.66-0.99; OR=0.64, 95%CI: 0.49-0.85). No significant relationship was observed in the multivitamin group. Supplemental folic acid doses of <400, 400, and >400 µg/d were related with reduced risk of PE (OR=0.62, 95%CI: 0.42-0.91; OR=0.81, 95%CI: 0.66-0.99; OR=0.68, 95%CI: 0.49-0.94). After stratified by pre-pregnancy BMI, pregnant women who used folic acid supplementation, those with pre-pregnancy BMI<24.0 kg/m(2) had reduced risk of PE (OR=0.75, 95%CI: 0.59-0.96). However, no significant relationship was observed in women with pre-pregnancy BMI≥24.0 kg/m(2). Conclusions: Folic acid supplementation before and during pregnancy were related with reduced risk of PE. Pre-pregnancy BMI might affect the relationship between folic acid supplementation and the risk of PE. Appropriate folic acid supplementation should be recommend for women with different pre-pregnancy BMI.