The study, published in the journal Pediatrics, found that women who smoked anytime during the month before pregnancy to the end of the first trimester were more likely to give birth to infants with certain congenital heart defects compared to women who did not smoke during this period.
Margaret Honein of the Centers for Disease Control and Prevention's National Center for Birth Defects and Developmental Disabilities said the association was stronger for mothers who reported heavier smoking during this time frame.
"Most people know that smoking causes cancer, heart disease and other major health problems," Honein said in a statement. "The indisputable fact is that women who smoke during pregnancy put themselves and their unborn babies at risk for other health problems."
This study included 3,067 infants with congenital heart defects and a comparison group of 3,947 infants with no major birth defects.
Septal heart defects -- a hole in the heart between the left and right heart chambers, which disrupts the flow of blood and oxygen to the body -- were the most common cardiac defect.
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