(RxWiki News) Moms-to-be who are both overweight and smokers are more than twice as likely to have a baby with a congenital heart defect than women who are either overweight or a smoker but not both.
Even though congenital heart defects occur in approximately eight newborns for every 1,000 born, doctors only tend to find a cause in about 15 percent of those cases.
"Don't smoke while pregnant."
But a new study reveals that quitting smoking or losing enough weight to bring their body mass index (BMI) below 25 might reduce their risks of giving birth to a baby with a heart problem.
The study was led by Dr. Marian Bakker, of the Department of Medical Genetics at the University Medical Centre in the Netherlands.
Bakker and colleagues analyzed the records of nearly 800 babies born between 1997 and 2008 with congenital heart defects but no other abnormalities.
They compared this data to that of 322 children with chromosomal abnormalities but with no heart defects.
Even when they controlled for mothers' education levels and alcohol consumption, they found the double whammy of smoking and being overweight posted much greater risks to the baby than either factor by itself.
Women with a body mass index (BMI) at 25 or higher who also smoked while pregnant had a two and a half times greater chance of having a baby with a congenital heart defect than women who only smoked or were only overweight but were not both.
"These results indicate that maternal smoking and overweight may both be involved in the same pathway that causes congenital heart defects," write the authors.
Babies were over three times more likely to be born with a defect where the blood flow to their aorta was blocked or decreased if their mother was overweight and smoked while pregnant.
The authors added that this increased risk of heart defects in the infant is part of a longer list of other problems that research have found associated with overweight pregnant women who smoke.
Other problems associated with these risk factors include miscarriages, premature birth and slowed growth in the baby.
This study appeared online in January in the journal Heart. The authors declared no conflicts of interest. The study was funded by the Dutch Ministry of Health, Welfare and Sports.