Mar 8, 2011

Smoking in Early Pregnancy Linked to Infant Heart Defects

Smoking in early pregnancy may raise the risk for certain congenital heart defects (CHD) in infants, according to the results of an analysis from the Baltimore-Washington Infant Study reported online February 28 and in the March print issue of Pediatrics.

“Maternal smoking during pregnancy has been implicated as a possible risk factor for birth defects, but the evidence is mixed, and when identified as a risk factor, the magnitude of the estimates has been typically modest,” write Clinton J. Alverson, MS, from the Division of Birth Defects and Developmental Disabilities, National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, and colleagues. “We investigated associations between maternal cigarette smoking during the first trimester and the risk of …CHDs among the infants.”

In the Baltimore-Washington Infant Study, which was the first US population-based case-control study of CHDs, case and control newborns were enrolled from 1981 to 1989. Mothers with overt pregestational diabetes were excluded from the analysis, as were case mothers whose infants had noncardiac anomalies, except for atrioventricular septal defects accompanying Down’s syndrome. Therefore, the analysis included a total of 2525 case and 3435 control infants.

In-person interview after delivery allowed determination of self-reported first-trimester maternal cigarette consumption. Logistic regression models were used to evaluate associations for 26 different groups of CHDs with maternal cigarette smoking. Odds ratios (ORs) were estimated for an increase in 20 cigarettes per day.

Self-reported first-trimester maternal cigarette consumption was statistically significantly and positively associated with the risk for secundum-type atrial septal defects (OR, 1.36; 95% confidence interval [CI], 1.04 -1.78), right ventricular outflow tract defects (OR, 1.32; 95% CI, 1.06 -1.65), pulmonary valve stenosis (OR, 1.35; 95% CI, 1.05 – 1.74), truncus arteriosus (OR, 1.90; 95% CI, 1.04 – 3.45), and levo-transposition of the great arteries (OR, 1.79; 95% CI, 1.04 – 3.10). Among infants without Down’s syndrome, there was a suggestive association for atrioventricular septal defects (OR, 1.50; 95% CI, 0.99 – 2.29).

“Women who smoke and are thinking about becoming pregnant need to quit smoking and, if they’re already pregnant, they need to stop,” said Thomas R. Frieden, MD, MPH, director of the CDC, in a news release. “Quitting is the single most important thing a woman can do to improve her health as well as the health of her baby.”

“Successfully stopping smoking during pregnancy also lowers the chances of pregnancy complications such as preterm delivery and that an infant will have other complications such as low birth weight,” said senior author Adolfo Correa, MD, PhD, medical officer in CDC’s National Center on Birth Defects and Developmental Disabilities.

The investigators note that their findings were not entirely consistent with those of previous studies, which may result from differences in the classification of exposures, time, and geography.

“Results of this study, based on a population-based design with high-quality case ascertainment and defect classification, add to the existing body of evidence that implicates first-trimester maternal cigarette smoking as a modest risk factor for select congenital heart defect phenotypes,” the study authors conclude.

The contents of the journal article are solely the responsibility of the authors and do not necessarily represent the views of the CDC. The study authors have disclosed no relevant financial relationships.

Pediatrics. Published online February 28, 2011. Abstract

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