Pregnant women who are overweight and smoke risk damaging the developing hearts of their unborn children, a new study has found.
Researchers, reporting in the journal Heart, based their findings on an analysis of nearly 800 babies born with congenital heart abnormalities, but no other defects, between 1997 and 2008. They compared those babies with 322 other children who were born with chromosomal abnormalities, but without any heart defects.
In comparing the two groups of babies, they found “an enhanced damaging effect” in children born to women who were both overweight and smoking during pregnancy.
They found the combined effects of overweight and tobacco were far more damaging to their developing babies than either factor alone, researchers said. In fact, overweight moms who also smoked during pregnancy were more than 2.5 times as likely to have a child with a congenital heart defect as women who either smoked or were overweight, but not both.

Congenital heart abnormalities are some of the most common defects found at birth, striking about eight in every 1000 babies, researchers noted.

"These results indicate that maternal smoking and overweight may both be involved in the same pathway that causes congenital heart defects," write the authors.

The findings add to the growing body of evidence linking smoking and overweight during pregnancy to a range of maladies – including miscarriage, stillbirths, stunted growth and premature birth, said the authors.