Passive, Active Smoking Both May Affect Fetus


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 conducted by Stephen G. Grant, Ph.D., of the University of Pittsburgh.

“This 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.

In an interview, he said, “The women who go to the trouble of quitting smoking feel they have taken care of the problem. 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.

The analysis examined data from two contradictory studies 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 levels of induced mutation among children of exposed women (active smokers, women who had quit smoking when they learned 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 mothers were both 0.87. The median for those who had quit smoking was 0.91, and for unexposed women, 0.60 (BMC Pediatr. 2005;5:20 [Epub ahead of print]).

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