POPULATION-BASED CASE-CONTROL STUDY OF FOLIC-ACID SUPPLEMENTATION DURING PREGNANCY

Previous studies have demonstrated that periconceptional folic acid/mu ltivitamin supplementation reduced the occurrence of neural tube defec ts. A case control analysis has been conducted in the dataset of the H ungarian Case Control Surveillance of Congenital Abnormalities, 1980-1 991. In the study period, 54.9% of 30 663 pregnant women who had healt hy babies (negative control group) were supplemented with high doses ( in general 2x3 mg) of folic acid per day. In those 17,300 pregnant wom en who had offspring with congenital abnormalities, the rate of folic acid supplementation was 50.4%. Exposure histories: preconceptional, I , II, III, and IV-IX post-conceptional months were determined by recor d reviews and questionnaire assessment. The case control pair analysis showed a significant protection after folic acid supplementation duri ng the critical period of cardiovascular defects, neural tube defects, cleft lip with oi without cleft palate and posterior cleft palate. (C ) 1996 Wiley-Liss, Inc.