Researchers have shown that risk for congenital anomalies is highest among babies born to older women who smoke.

The authors of this study used birth certificate data and hospital discharge records from Washington state to determine if maternal smoking during the first trimester of pregnancy is linked to heart defects and if so, what types of defects.

Lead author Patrick M. Sullivan, MD, FAAP, clinical fellow in pediatric cardiology at Seattle Children's Hospital and a master's student in epidemiology at the University of Washington School of Public Health, said I care for kids with complex congenital heart disease on a daily basis, and I see these kids and their families enduring long hospitalizations and often sustaining serious long-term complications as a result of their disease.

Sullivan said usually, the cause of a heart defect is unknown. I saw this research as an opportunity to study what might be a preventable cause of congenital heart defects.

Using hospital discharge records, researchers identified 14,128 children born with a variety of heart defects from 1989-2011. They matched these cases to 62,274 children without heart defects born in the same year.

Then, they compared the proportion of children with heart defects whose mothers reported smoking during pregnancy to the proportion of children without heart defects whose mothers smoked. Mothers' smoking status, as well as how much they smoked daily, was available from birth certificates.

Newborns whose mothers smoked were at about a 50 to 70 percent greater risk for anomalies of the valve and vessels that carry blood to the lungs (pulmonary valve and pulmonary arteries) and about a 20 percent greater risk for holes in the wall separating the two collecting chambers of the heart (atrial septal defects). All of these defects often require invasive procedures to correct.