Maternal prepregnancy weight and congenital heart defects in offspring.

To determine the relation between having an infant with a major heart defect and a mother's prepregnancy weight, we compared 1,049 Atlanta-area women who gave birth to liveborn or stillborn infants, each with a major heart defect, with 3,029 Atlanta-area women who gave birth to infants without birth defects. The infants of control women were randomly selected from birth certificates and were frequency-matched to the case group by race, birth hospital, and birth period from 1968 through 1980. After excluding diabetic mothers and adjusting for potential confounders, compared with average-weight women (body mass index 19.9--22.7), we found that underweight women (body mass index <16.5) were less likely to have a child with a major isolated heart defect [odds ratio (OR) = 0.64; 95% confidence interval (CI) = 0.43--0.97], whereas the OR was elevated among overweight or obese women (body mass index >26) (OR = 1.36; 95% CI = 0.95--1.93). Using average-weight women who did not take periconceptional multivitamins as the reference group, periconceptional multivitamin use was associated with a reduced OR for isolated heart defects among average-weight women (OR = 0.61, 95% CI = 0.36--0.99) and underweight women but not among overweight or obese women (OR = 1.69, 95% CI = 0.69--3.84).