Women who smoke early in their pregnancy are more likely to give birth to children with congenital heart defects (CHD), according to a new study.

HealthDay News reported Nov. 14 that a study involving 566 infants with CHD, 491 children without the disease, and their parents found that women who smoked any time between a month prior to conception and the end of the first trimester of pregnancy were 60 percent more likely to have children with CHD. Researchers added that exposure to secondhand smoke early in pregnancy also appeared to increase CHD risk.

"The heart's basic structures develop very early in pregnancy, before many women realize they are pregnant," said study author Sadia Malik of the University of Arkansas for Medical Sciences in Little Rock. "Thus, even if a woman quits smoking at six weeks or later, her fetus will still have been exposed to the harmful effects of cigarette smoking during cardiac development."

The research was presented at the American Heart Association's annual meeting in Chicago this week.