Being overweight during pregnancy significantly increases pregnancy complication risk. Smoking during pregnancy also increases pregnancy complication risk. According to a study published in the online journal, Heart, being overweight and smoking during pregnancy may be more dangerous than each factor as a standalone condition or choice.

The study examined nearly 800 infants and fetuses with congenital heart deformities with no known cause or associated defect. The 800 infants were compared with nearly 350 infants born with chromosome problems, but no heart defect. Researchers focused on heart deformities because about eight out of 1,000 infants are born with congenital heart deformities, but causes are found in less than 20-percent of cases.

When the two groups were compared, researchers found a significant increase in heart deformities in infants and fetuses belonging to mothers who were both overweight and smoked during pregnancy. The risk of heart defect was greater in women who fell into both groups rather than one group or the other. If the pregnant women had a BMI of 25 or greater and she smoked, heart defects were 2.5 times more likely to occur, compared to women who smoked or women who were overweight as individual groups.

One specific heart defect, outflow tract obstructive deformities, was particularly more prominent in the overweight smoking group with an increased risk 3 times greater in the test group. According to the authors of the study, “These results indicate that maternal smoking and overweight may both be involved in the same pathway that causes congenital heart defects.”

The findings of the study prove that smoking and being overweight during pregnancy are significant risk factors individually, but when paired together could be the cause of some cases of unexplained heart defects. Further research on larger pools of participants is needed to narrow down specific heart deformities and risk rates associated with being overweight and a smoker during pregnancy.

Source: Maria E Baardman, Wilhelmina S Kerstjens-Frederikse, Eva Corpeleijn, Hermien EK de Walle, Robert MW Hofstra, Rolf MF Berger, Marian K Bakker. Heart. 20 January, 2012.