Periconceptional folic acid fortification for the risk of gestational hypertension and pre-eclampsia: a meta-analysis of prospective studies

Published literatures report controversial results about the association of folic acid-containing multivitamins with gestational hypertension and pre-eclampsia. A comprehensive search was performed to identify related prospective studies to assess the effect of folic acid fortification on gestational hypertension and pre-eclampsia. The Q test and I-2 statistic were used to examine between-study heterogeneity. Fixed or random effects models were selected based on study heterogeneity. A funnel plot and modified Egger linear regression test were used to estimate publication bias. Eleven studies conformed to the criteria. Pooled results indicated that folic acid fortification alone was not associated with the occurrence of gestational hypertension [relative risk (RR)=1.03, 95% confidence interval (CI): 0.98-1.09, P=0.267] and pre-eclampsia (RR=0.99, 95% CI: 0.90-1.08, P=0.738). However, supplementation of multivitamins containing folic acid could prevent gestational hypertension (RR=0.57, 95% CI: 0.43-0.76, P<0.001) and pre-eclampsia (RR=0.64, 95% CI: 0.48-0.84, P=0.001). The difference between folic acid fortification alone and multivitamins containing folic acid was significant. This meta-analysis suggests that periconceptional multivitamin supplementation with appropriate dose, not folic acid alone, is an appropriate recommendation for pregnant women. The effect should be further confirmed by conducting large-scale randomised controlled trials.