A study by the Centers for Disease Control and Prevention in Atlanta found tobacco exposure is associated with a 20 percent to 70 percent increased risk of certain types of defects such as those that obstruct the flow of blood from the right side of the heart into the lungs and openings between the upper chambers of the heart.
"Women who smoke and are thinking about becoming pregnant need to quit smoking and, if they're already pregnant, they need to stop," Dr. Thomas R. Frieden, director of the CDC, says in a statement.
"Quitting is the single most important thing a woman can do to improve her health as well as the health of her baby."
The findings, published in the journal Pediatrics, are based on a large U.S. population-based case-control study of congenital heart defects involving 2,525 case and 3,435 control infants born from 1981 to 1989.
If women quit smoking before or early in pregnancy, as many as 100 cases of right ventricular outflow tract obstructions and 700 cases of atrial septal defects could be eliminated each year in the United States, the study says.