Smoking, genes tied to birth weight
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, researchers reported recently.
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 5 pounds, 8 ounces or less--have higher death rates and are more susceptible to health problems during infancy and childhood. Smoking has been associated with low birth weight in previous studies, and pregnant women are advised not to smoke.
The Boston study, published in the Journal of the American Medical Association, was based on smoking habits of 741 women during pregnancies between 1998 and 2000.
In general, the women who smoked during the entire pregnancy bore children with a mean reduction in birth weight of 13.3 ounces. But the reduction was as much as 2 pounds, 12 ounces among women with certain variant genotypes.
"Although there is little published data on genetic susceptibility to cigarette smoke in relation to birth weight or gestation, we believe this susceptibility is biologically possible," said lead author Xiaobin Wang, an associate professor of pediatrics at the Boston school.
"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," she added.
"Our hope is that 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 [it] and infant mortality," she said.