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

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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 μmol/L), decreased plasma homocysteine (on average 0.39 μmol/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.

Section snippets

Materials and Methods

The Ottawa and Kingston (OaK) Birth Cohort recruited nontransferred, consenting women between 12-20 weeks’ gestation during their prenatal visit at the Ottawa Hospital and Kingston General Hospital. The current analysis included subjects from phase I of the OaK Birth Cohort, which started in October 2002 and ended in December 2005. The research nurses explained to pregnant women the purpose of the study, what would be expected from them, and what they could expect from the study. For

Results

A total of 4024 women were approached to participate in the study; 3134 (78%) agreed and were recruited. Among them, 70 women were excluded because of twin births and 113 women were excluded because of missing information such as gestational age at delivery, birthweight, or sex (59) and lost to follow-up because of the participant’s relocation outside the study center (54), leaving 2951 subjects for final analysis.

Ninety-two percent of the study subjects were taking folic acid supplementation

Comment

Our prospective cohort study in a cohort of Canadian women found that 92% had supplementation with folic acid or multivitamins containing folic acid in the early second trimester, and among them, most (>95%) had a supplementation of 1.0 mg or higher, twice the recommended level for the prevention of neural tube defects by Health Canada.12

Supplementation of multivitamins containing folic acid was associated with increased serum folate, lowered plasma homocysteine, and reduced risk of

Acknowledgments

We acknowledge the following people because without their commitment and expertise, this project would not have been possible: the OMNI Research Nurse Group (Ottawa and Lucy Chura, RN, BScN, study coordinator, Queen’s Perinatal Research Unit research team (Queen’s Perinatal Research Unit Kingston and Lizy Kodiattu, MD); Dr. George Tawagi and team (Ottawa Hospital–Civic Campus); and Carol Ann Jodouin, Department of Laboratory Medicine, Ottawa Hospital.

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    Cite this article as: Wen SW, Chen X-K, Rodger M, et al. Folic acid supplementation in early second trimester and the risk of preeclampsia. Am J Obstet Gynecol 2008;198:45.e1-45.e7.

    Supported in part by a grant from the Canadian Institute for Health Research (Grant MOP 53188). S.W.W., G.N.S., R.J.S., and M.C.W. are recipients of a New Investigators’ Award from the Canadian Institute for Health Research. M.R. is a Clinical Investigator of the Heart and Stroke Foundation of Canada, and X.-K.C. and Q.Y. are Canadian Institute for Health Research/Strategic Training Initiatives of Research in Reproductive Health Sciences postdoctor fellows.

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