Lack of periconceptional vitamins containing Folic Acid And diabetes mellitus - Associated birth defects. Does the lack of use of periconceptional vitamins or supplements that contain Folic Acid and diabetes mellitus increase the risk of birth defects? The National Birth Defects Prevention Study (1997-2004), used a population-based case-control study of birth defects to examine the effects of preexisting diabetes mellitus and the absence of periconceptional intake of vitamins that contain folic acid leading to birth defects. 14,721 case infants and 5437 controlled infants selected for the study. Case infants were categorized as having at least 1 eligible birth defect and were live born, still born, or electively terminated. Controlled infants were live born infants without birth defects who were selected either from hospital birth records or birth certificates. Clinical information on case infants were reviewed by a team of clinical geneticists. With the restriction to analyze mothers with preexisting diabetes mellitus (type 1 or type 2). The study evaluated the independent and joint effects by comparing the risk for birth defects among 4 exclusive grouping of mothers. (1) mothers without preexisting diabetes mellitus with intake of folic acid containing vitamins; (2) mothers with preexisting diabetes mellitus with the intake of vitamins; (3) mothers without preexisting diabetes mellitus with no intake of vitamins, and (4) mothers with preexisting diabetes mellitus with no intake of vitamins. The mothers would be asked to report their use of any vitamins or supplements containing folic acid, including information on the product, and the frequency of use. Multiple logistic regressions were used to conduct their findings. The intervals were calculated based on expansions of the variances and covariance. Case and control mothers differed in many characteristics, from body mass index, maternal age, race or ethnicity, education, parity,
References: Andersson T, Alfredsson L, Kallberg H, Zdravkovic S, Ahlborn A, Calculating measures of biological interactions. Eur J Epidemiol 2005; 20:575-9