Periconceptional multivitamin folic acid use, dietary folate, total folate and risk of neural tube defects in South Carolina.
OBJECTIVE
To investigate whether dietary folate or multivitamin folic acid taken 3 months before conception and during the first 3 months of pregnancy reduces the risk of isolated occurrent neural tube defect (NTD)-affected pregnancies.


METHODS
This population-based case control study conducted between 1992 and 1997 included 179 women with NTD-affected pregnancies and 288 randomly selected controls. Women completed a food frequency questionnaire and were interviewed about lifestyle behaviors, pregnancy histories and use of multivitamins.


RESULTS
Use of 0.4 mg or more of multivitamin folic acid at least 3 times per week during the periconceptional period showed no statistically significant reduction in NTD risk [adjusted odds ratio (AOR) = 0.55, 95% confidence interval (CI) = 025, 1.22]. After adjusting for covariates, protective effects for NTDs were observed at the highest quartiles of dietary folate and total folate (daily dietary folate plus daily multivitamin folic acid); the respective odds ratios were 0.40 (95% CI = 0.19, 0.84) and 0.35 (95% CI = 0.17, 0.72).


CONCLUSIONS
This study illustrates some of the difficulties in determining effects of folic acid and dietary folate in a population where the consumption of foods rich in folate and the use of multivitamins are increasing and the rate of NTDs is declining. Studies are needed to monitor future changes in folate levels and their effect on health.
Thompson
Shirley J
SJ
Department of Epidemiology and Biostatistics, Norman J. Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, USA.
Torres
Myriam E
ME
Stevenson
Roger E
RE
Dean
Jane H
JH
Best
Robert G
RG
D000328:Adult; D016022:Case-Control Studies; D019587:Dietary Supplements; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage / Q000627:therapeutic use*; D006801:Humans; D038801:International Classification of Diseases; D007407:Interviews as Topic; D016015:Logistic Models; D009436:Neural Tube Defects / Q000453:epidemiology / Q000517:prevention & control*; D016017:Odds Ratio; D016742:Preconception Care / Q000379:methods*; D011247:Pregnancy; D011295:Prenatal Care / Q000379:methods*; D012307:Risk Factors; D013022:South Carolina / Q000453:epidemiology; D014815:Vitamins / Q000008:administration & dosage / Q000627:therapeutic use
D014815:Vitamins; D005492:Folic Acid