(RxWiki News) It's not news that smoking during pregnancy is a bad idea. But researchers are still learning the various ways it can affect a developing baby.
A recent study found that newborns were more likely to have heart defects if their mothers smoked during pregnancy than if their mothers didn't.
Further, the more cigarettes the mother smoked while pregnant, the more the child's risk of a heart birth defect increased.
Another factor adding to a child's risk of a heart birth defect was having a mother who smoked and was older than age 35.
"Don't smoke during pregnancy."
This study, led by Patrick Sullivan, MD, a clinical fellow in pediatric cardiology at Seattle Children's Hospital, looked at the risk of heart defects among women who smoked during pregnancy.
The researchers investigated the medical records and birth certificates of 76,402 newborns and their mothers, including 14,128 babies born with heart defects and 62,274 babies born without heart defects and used them as a comparison group.
The researchers considered which mothers had smoked during their first trimester of pregnancy, how many cigarettes a day they smoked and what other risk factors for a child's heart defect the mothers may have had.
Overall, the researchers found the mothers had about 1.2 times, or 20 percent, greater odds of having a child with a heart birth defect if the mothers smoked than if they didn't.
In particular, smoking mothers' children had 1.5 times greater odds of having pulmonary valve anomalies, 1.7 times greater odds of pulmonary artery anomalies and 1.4 times greater odds of isolated atrial septal defects.
All of these problems are different kinds of heart defects that a baby can be born with.
The researchers also found that the more cigarettes the mothers smoked, the higher the risk was that her child would be born with a heart defect.
For example, the risk of a heart defect in children of women who smoked more than 20 cigarettes a day was 1.6 times greater than in children of nonsmokers.
Yet the risk of heart defects in children of mothers who smoked one to 10 cigarettes a day while pregnant was only 1.15 times greater than the risk in children of nonsmokers.
The risk of a heart defect among newborns was also greater in older smoking mothers (over age 35) than in younger ones.
For example, the risk of heart defects in children of mothers who were 35 or older and smoked more than 20 cigarettes a day was twice as much as in nonsmoking mothers' children.
Yet among children of mothers under age 35 and smoking more than 20 cigarettes a day, the increased risk was 1.5 times greater than among children of nonsmoking mothers.
Overall, however, it was clear that smoking during pregnancy was linked to a slightly increased risk of heart defects, the researchers concluded.
This study has not yet been published in a peer-reviewed journal, and its findings should be interpreted with caution.
The research was presented May 3 at the Pediatric Academic Societies annual meeting in Vancouver, Canada.
No outside funding was used for this study, and no information regarding disclosures or possible conflicts of interest were available.