A pregnant woman's exposure to secondhand cigarette smoke may be just as risky to the fetus as is active smoking, according to a pooled data reanalysis by Stephen G. Grant, Ph.D., of the University of Pittsburgh.
“This [new] analysis shows not only that smoking during pregnancy causes genetic damage in the developing fetus that can be detected at birth, but also that passive, or secondary, exposure causes just as much damage as active smoking, and it's the same kind of damage,” Dr. Grant said in a statement.
“The women who go to the trouble of quitting smoking feel they have taken care of the problem,” he said in an interview. “This is a cautionary exercise in which we say women have to change their lifestyles in other ways” such as having their husbands quit smoking and not going outside with their friends on smoke breaks even if they don't smoke themselves. “You have to protect your baby from passive exposure as much as from active smoking,” he said.
The study examined data from two contradictory studies published in the mid-1990s on rates of mutation at the HPRT locus (a measure of in vivo mutagenesis) in newborn cord blood samples. Compared with samples from babies who had not been exposed to smoke in utero, exposed babies had significantly higher mutation rates. There were no significant differences in the levels of induced mutation among children of exposed women (active smokers, women who had quit smoking when they found out they were pregnant, and women who were only passively exposed to smoke).
In the pooled data, the median HPRT mutation frequencies for actively and passively smoking moms was identical at 0.87 (BMC Pediatr. 2005;5:20 [Epub ahead of print]).