WASHINGTON (Reuters) – Women who are overweight or obese when they get pregnant are more likely to give birth to children with congenital heart defects, according to a US government study.

The study, conducted by the US Centers for Disease Control and Prevention, concluded that women who were overweight or obese at the time they became pregnant were 18 percent more likely to give birth to babies with heart defects, while severely obese women had a 30 percent increased risk.

The babies had problems including obstructive defects on the right side of the heart and defects in the tissue separating the heart's two upper chambers, the researchers reported in the American Journal of Obstetrics and Gynaecology.

"Congenital heart defects are the most common types of birth defect, and among all birth defects, they are a leading cause of illness, death and medical expenditures," said Dr. Edwin Trevathan, a CDC expert on birth defects and developmental disabilities. The CDC, the US government's disease watchdog, recommends that overweight women work with their doctors to achieve a healthy weight before pregnancy.

Researchers examined the health of 6,440 infants with congenital heart defects and 5,673 infants without problems, all of whose mothers were interviewed as part of the CDC's National Birth Defects Prevention Study.