SATURDAY, May 3, 2014 (HealthDay News) -- New research suggests that mothers who smoke early in pregnancy put their unborn child at greater risk of heart defects, and the risk goes up as smoking increases.
It's not clear, however, if smoking directly causes the heart defects or if some other factors that the smoking women share may be responsible, the researchers said.
The findings add another condition to the long list of medical problems -- including cleft palates and other deformities -- that are more likely to affect the children of women who smoke while pregnant.
The researchers came to their conclusions after examining medical records from Washington state that included information about whether mothers smoked in the first trimester.
They examined the records of over 14,000 children with heart defects born from 1989-2011 and matched them to almost 62,300 healthy children born at the same time. The researchers then assessed the mothers' smoking habits, which were available from birth certificates.
"Usually, the cause of a heart defect is unknown," said study author Dr. Patrick Sullivan, a clinical fellow in pediatric cardiology at Seattle Children's Hospital. "I saw this research as an opportunity to study what might be a preventable cause of congenital heart defects," he said in a news release from the American Academy of Pediatrics.
Infants of mothers who smoked early in pregnancy were at higher risk of defects of the heart valve and vessels that carry blood to the lungs. They were also more likely to have holes in the wall separating the two collecting chambers of the heart, the study found. Some of these problems require invasive surgical repairs.
Smoking by mothers early in pregnancy may be responsible for 1 percent to 2 percent of heart defects, the researchers estimated. The association between smoking and heart defects was greater for older mothers, the study said.
The findings are to be presented Saturday at the annual meeting of the Pediatric Academic Societies in Vancouver, Canada.
Data and conclusions presented at meetings are typically considered preliminary until published in a peer-reviewed medical journal.
For more about birth defects in the heart, try the National Heart, Lung and Blood Institute.