A study in the US has shown that smoking and obesity in pregnancy can significantly increase the risk of the heart defects in new-born babies. The study, which was conducted by researchers at the University Medical Centre, Groningen, analysed 800 babies born with congenital heart disease between 1997 and 2008 and correlated the results with the risk factors of obesity and smoking in the babies’ mothers during pregnancy.

The results of the study showed that both smoking and obesity in pregnant women can increase the likelihood of babies being born with certain defects. Typical defects caused by smoking included valve and muscular abnormalities, while obesity was more closely linked with abnormalities of the septum and the upper and lower chambers of the heart. The results of the analysis revealed that while both smoking and obesity were significant risk factors in their own right, when women are both overweight and smoke during pregnancy, the risk of congenital heart disease in their new-borns is significantly increased.  In fact, when both risk factors were present in mothers, babies were 2.5 times more likely to have a heart defect at birth.

The study’s authors commented on their findings: "These results indicate that maternal smoking and overweight may both be involved in the same pathway that causes congenital heart defects”.

Statistics indicate that over 50% of women in the United States are obese, with a body mass index of 25 or over, when they become pregnant.