Folic acid supplementation in early second trimester and the risk of preeclampsia.

Objective: The objective of the study was to evaluate the association between folic acid supplementation in early second trimester and the risk of developing preeclampsia.

Study Design: We carried out a prospective cohort study between October 2002-December 2005. We recruited women who had their prenatal care visit (12-20 weeks' gestation) at the Ottawa Hospital and Kingston General Hospital. All charts for participants with a diagnosis of preeclampsia were audited and blindly adjudicated by 4 study investigators to validate the diagnosis.

Results: A total of 2951 pregnant women were included in the final analysis. Supplementation of multivitamins containing folic acid was associated with increased serum folate (on average 10.51 micromol/L), decreased plasma homocysteine (on average 0.39 micromol/L), and reduced risk of preeclampsia (adjusted odds ratio, 0.37; 95% confidence interval, 0.18-0.75).

Conclusion: Supplementation of multivitamins containing folic acid in the second trimester is associated with reduced risk of preeclampsia.