July 28, 2005
Thursday

It's not enough for a woman to stop smoking when she becomes pregnant, a new study suggests. To protect the developing fetus, other family members should stop smoking too, and expectant mothers should stop contact with anyone who smokes.

Pooling data from three earlier studies, Stephen G. Grant, an environmental and occupational health researcher at the University of Pittsburgh's Graduate School of Public Health, found that secondhand smoke leads to the same number of genetic mutations in newborns as does smoking by the mother herself.

As Grant put it: "Passive exposure gives you just as much of an exposure and just as bad damage as active smoking."

His findings were recently published in the online journal BMC Pediatrics.

In the earlier studies, umbilical cord blood samples from newborns were tested for changes in the HPRT gene, which is on the X, or female, chromosome.

The study compared gene mutation rates among babies born to mothers who smoked, quit smoking when they learned they were pregnant, lived or worked with smokers, or had no exposure to smoking.

"What we found is the three exposed groups were all pretty much the same," Grant said. "But they were all significantly different from the unexposed."

Mutations of the HPRT gene were almost twice as common in the exposed groups, he said.

"If the mutations are occurring at this gene, there's no reason why they shouldn't be occurring at the same elevated frequencies at other genes," Grant said. Depending on which genes are affected, those changes could ultimately lead to birth defects, cancer or other conditions.

Dr. Barry Finette, a pediatrician at the University of Vermont, led one of the studies Grant revisited. The Vermont work indicated a higher mutation rate in the passive smoking group, but did not include enough participants to verify the relationship was real.

The gene changes that were observed, however, "can indirectly be linked to the types of mutations that occur in children with leukemia," Finette noted.

Doctors should be advising the husbands of pregnant women to stop smoking, he said.

"There's no doubt about it," Finette said. "There is strong and growing evidence that secondary smoke causes clinical disease both in the recipient of it and in the fetus."

Pregnant women should do more than stub out their own cigarettes, Grant said.

"If you're going to plan a pregnancy, plan to be away from smokers," Grant advised. "The first present you can give to your baby is not exposing them in (the womb)."

He and his colleagues are working on a follow-up study that has more participants. The initial results indicate that alcohol use also leads to elevated mutation rates, he said.

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