Maternal Smoking and Congenital Heart Defects

Abstract

Congenital heart defects (CHDs) are the most frequent and serious structural birth defects in the United States. Affected infants who survive frequently require multiple operations, and many of them have life-long disability. One of the many risk factors proposed for CHDs is maternal smoking during pregnancy or exposure to environmental tobacco smoke (ETS). This population-based case-control study, the National Birth Defects Prevention Study, examined the association between maternal smoking and CHDs in 3067 infants with nonsyndromic cardiac defects and 3947 others without birth defects. Mothers were asked about smoking from 1 month before pregnancy through the first trimester. Logistic regression analysis served to compute odds ratios and 95% confidence intervals (CIs). Case infants were likelier than control infants to be born before term and had lower birth weights. Women who smoked at any time during the periconceptional period were more likely than nonsmokers to have an infant with an atrial or ventricular septal heart defect—the commonest malformation observed (40%). This relationship was independent of numerous potential confounding factors including vitamin use, alcohol intake, a family history of congenital heart disease, the mother’s race or ethnicity, and maternal age. The association with septal defects was stronger with exposure to medium (15 to 24 cigarettes per day) or heavy (≥25 cigarettes per day) smoking than with light (1 to 14 cigarettes per day) exposure. The OR for septal defects in heavy smokers was 2.06, with a 95% CI of 1.20–3.54. The risk of right-sided obstructive defects including pulmonary valve stenosis was also increased in infants whose mothers smoked, on average, 25 or more cigarettes a day. No association was apparent between exposure to ETS at home or at work and the risk of CHDs. For mothers who smoked, there was no apparent additional risk from exposure to ETS.