Periconceptional vitamin use, dietary folate and occurrent neural tube defected pregnancies in a high risk population

Abstract

PURPOSE: This 5 year (1992–1997) population-based case control study was conducted to determine if supplemental or dietary folate taken during the periconceptional period reduces the risk of occurrent neural tube defect (NTD) affected pregnancies in a high risk population.METHODS: Cases were all NTD pregnancies including elective terminations, fetal deaths and live births in South Carolina. Only isolated, occurrent NTD affected pregnancies were included (N = 179). Controls (N = 288) were randomly selected from each hospital in proportion to the hospital's contribution to the total live births in the state for the previous year. All mothers were interviewed in person using a modified Centers for Disease Control and Prevention Birth Defect Risk Factor Surveillance Mother's Questionnaire and the Harvard Food Frequency Questionnaire.RESULTS: Women who used a vitamin with 0.4 mg or more of folate at least 3 times per week during the 3 months before and 3 months after conception had a lower risk of having an NTD affected pregnancy than women who took no folate supplementation at any time during pregnancy [adjusted odds ratio (AOR) = 0.42; 95% confidence interval (CI) = 0.19–0.94]; women who used a vitamin with 0.4 mg or more of folic acid for less than 3 times per week or in partial months during the 6 month periconceptional period also had a slightly lower risk of having an NTD affected pregnancy relative to women who used no folate supplementation at any time during pregnancy [AOR = .72; 95% CI = 0.41–1.30]. The risk of NTD affected pregnancy was also lower for women who daily consumed foods containing higher levels of folate: AORs were 0.36 (95% CI = 0.18–0.73), 0.72 (95% CI = 0.42–1.22), and 0.61 (95% CI 0.36–1.04) from the highest to lowest quartile of dietary folate which were 0.457–3.12 mg, 0.322–0.457 mg, and 0.236–0.322 mg respectively.CONCLUSIONS: A reduction in occurrent NTD risk associated with folate supplementation and dietary intake was observed.