PERICONCEPTIONAL MULTIVITAMIN USE IN RELATION TO THE RISK OF CONGENITAL URINARY-TRACT ANOMALIES

To study the relation of maternal periconceptional vitamin use to the risk of a congenital urinary trace anomaly (CUTA), we conducted a case -control study using the Washington State Birth Defect Registry. We id entified CUTA cases with no known chromosomal abnormality in seven cou nties in western Washington State occurring between January 1, 1990, a nd December 31, 1991. We randomly selected a sample, as controls, of a ll infants delivered in five large hospitals in King County who did no t have a birth defect and who were born in the same year as the cases. About 55% of all infants in King County and a smaller proportion of i nfants in the other six counties are delivered in these five hospitals . We interviewed mothers of 118 cases and 369 controls to obtain infor mation about their vitamin use during the pregnancy and during the yea r before the conception. After adjustment for maternal race, family in come, county of maternal residence, and birth year, we found that wome n who used multivitamins during the first trimester had only 15% the r isk of bearing a child with a CUTA compared with women who did not tak e vitamins [odds ratio (OR) = 0.15; 95% confidence interval (CI) = 0.0 5-0.43], The reduction was smaller for use restricted to the second or third trimesters (OR = 0.31; 95% CI = 0.09-1.02). Among women who use d vitamins during the first trimester, vitamin use before conception w as not associated with any further reduction in the risk, nor did ther e appear to be an association with the amount or brand of vitamin used . Restricting the analysis to residents of King County did not change the results. Our results indicate that prenatal multivitamin use, part icularly during the first trimester, may reduce the risk of a CUTA. Be cause all of the preparations taken by study participants contained ma ny vitamins as well as folic acid, it was not possible to identify whi ch one (or several) chemical(s) may have been responsible for the redu ced risk of a CUTA.