Women who smoke during pregnancy are more likely to bear an underweight child, but some women may carry a higher risk than others because of genetic susceptibility. The finding could help medicine better determine the causes of low birth weight, though the researchers said they were not recommending at this point that women be screened for presence of the genes involved.
"Our data demonstrate that a subgroup of pregnant women with certain genotypes appeared to be particularly susceptible to the adverse effect of cigarette smoke, suggesting an interaction between metabolic genes and cigarette smoking" said the report from Boston University School of Medicine.
Low birth weight babies -- those born at about five pounds or less -- have higher death rates and are more susceptible to a number of other health problems during infancy and childhood. Cigarette smoking has been associated with low birth weight in a number of previous studies, and women are advised not to smoke during pregnancy. In general, the women who smoked during the entire pregnancy bore children with a mean reduction in birth weight of 13.3 ounces (377 grams). But the reduction was as much as two pounds, 12 ounces (1,285 grams) among women with certain variant genotypes.
Low birth weight is a very complex entity and many environmental and genetic factors may be involved. This study is the first step to understand how genetic susceptibility interacts with environmental exposures to affect infant birth weight. This study will open up new areas of research that will lead to better understanding of the causes of low birth weight and ultimately lead to reducing the tragedy of infant mortality.