Genes can triple smoking's damage to unborn baby
Variations in two genes can triple the damage done to your unborn baby if you smoke during your pregnancy, Boston University researchers report. These variations can cause both premature delivery and low birth weight.
Two genes make smoking even more damaging
The two genes produce enzymes that metabolize the byproducts of cigarette smoke, and both come in different forms. A new study of 741 women shows that in each case, one form of each gene somehow makes smoking much more damaging, increasing the incidence of premature delivery and low birth weight.
"It is certainly too early to make clinical applications of these findings," says Dr. Xiaobin Wang, associate professor of pediatrics and leader of the group reporting the results in tomorrow's issue of the Journal of the American Medical Association.
Instead, she says, "our study represents the first step in estimating how genes react with environmental exposures to impact the incidence of low birth weight."
Pregnant women should not smoke at all
The study certainly does not affect the standing advice that pregnant women should simply not smoke, Wang says. "Maternal cigarette smoking is harmful to all women," she says. "It is even more harmful in a set of women with certain genotypes."
Gene increases low birth weight chances by 70 percent
For example, women who smoked had a 30 percent increased incidence of having a baby with abnormally low birth weight than non-smokers if they had one version of the gene designated CYP1A1, but the risk more than tripled when they carried the other version of the gene. The risk was increased by 70 percent for smoking women who carried one version of the gene designated GSTTI, but that risk was also was more than tripled for those carrying the other version. There were similarly increased risks of premature delivery for both versions of both genes.
"Our hope is that this work will open new areas of research leading to a better understanding of the causes of low birth weight, and hopefully to reduce the impact of low birth weight," Wang says.
In the future, "the opportunity might be there to be able to identify people who are at high risk for an adverse outcome," says George P. Vogler, professor of bio-behavioral health at Pennsylvania State University.
Gene-testing not practical yet
"Testing for genes is not practical right now," Vogler says. "But the cost of doing the test is dropping constantly, and it may become cost-effective at some point."
Such tests might not necessarily be just for genes related to smoking, Wang says.
"This study is part of an ongoing evaluation of the environmental and genetic determinants of low birth weight," she says. "We will be looking at other genes involved in alcohol metabolism, nutrition and other factors known to affect birth weight. We have a multi-disciplinary research team, and will investigate those one by one."