TUESDAY, Jan. 31, 2012 (HealthDay News) -- Women who are both overweight and smoke during pregnancy could damage their baby's developing heart, a new study warns.
Researchers in the Netherlands looked at nearly 800 fetuses and babies with congenital heart defects, but no other birth defects, between 1997 and 2008. Congenital means present at birth. This group was compared with more than 300 fetuses and babies born with chromosomal abnormalities, but without any heart defects.
The results showed that women who were both overweight (body mass index of 25 or more) and smoked during pregnancy were 2.5 times more likely to have a baby with a congenital heart defect than women who either smoked or were overweight during pregnancy.
The researchers also found that babies born to overweight mothers who smoked during pregnancy had a threefold increased risk of outflow tract abnormalities, in which blood flow from the ventricles of the heart to the pulmonary artery or aorta is reduced or blocked.
The study was published online Jan. 31 in the journal Heart.
"These results indicate that maternal smoking and overweight may both be involved in the same pathway that causes congenital heart defects," wrote Dr. Marian Bakker of the department of medical genetics at the University Medical Centre, Groningen, and colleagues in a journal news release.
The findings add to the growing body of evidence that smoking and being overweight during pregnancy is associated with problems such as miscarriage and stillbirth, stunted growth and premature birth, the researchers said.
Heart abnormalities, one of the most common kinds of birth defects, affect about 8 in every 1,000 babies. A likely cause is identified in only 15 percent of cases.
The March of Dimes has more about heart defects.