Smoking cigarettes just before becoming pregnant and shortly thereafter may increase a woman’s risk of having a baby with a congenital heart defect by 60 to 80 percent, according to a report presented Tuesday at a meeting of the American Heart Assn. in Chicago.

And women who are exposed to secondhand smoke in the workplace or at home also may increase their risk of bearing infants with such defects, said Dr. Sadia Malik, a pediatric cardiologist at the University of Arkansas for Medical Sciences, the study’s lead author.

“We found a 30 percent higher risk of having a child with congenital heart disease if you’re exposed to cigarette smoke at home or the workplace,” she said.

The heart association estimates that 35,000 infants are born each year with congenital heart defects that range from mild to life-threatening. Although the causes of most defects are not known, scientists believe genetic susceptibilities and exposure to environmental toxins, such as alcohol, infections, various chemicals and some medications, play major roles.