Smoking can damage fetal genes

Smoking during pregnancy increases the risk of causing genetic damage to the unborn child, a preliminary study in yesterday’s Journal of the American Medical Association suggests.

The key finding in the report by Spanish researchers was that there was a 3-fold increase in structural chromosomal abnormalities in fetal cells from pregnant smokers than those from nonsmokers.

“Such results, if substantiated, would provide direct evidence of tobacco-associated” genetic mutations and “could have important implications for the immediate and long-term health effects of children born to mothers who smoke,” Environmental Protection Agency scientists David M. DeMarini and R. Julian Preston wrote in an accompanying editorial.

The EPA scientists and the European researchers — biologists with the Universitat Autonoma de Barcelona in Bellaterra, Spain — stressed there already was a lot of evidence indicating the hazards of smoking while pregnant.

But until now, only “indirect data” indicating smoking has a possible “genotoxic effect” on human pregnancies has been published, said Rosa Ana de la Chica, who led the Spanish team of researchers. Genotoxic refers to the potential for tobacco to damage DNA and cause genetic mutations.

Mr. DeMarini and Mr. Preston said the new study is the first to provide direct evidence of such a link. But, Mr. DeMarini cautions that the Spanish research is “not a definitive study,” and he questions some of the methodology used.

He said the experiment could have been better if the scientists relied on an “independent assessment of a woman’s smoking behavior, not just her memory.”

The new study analyzed amniocytes, or cells of fetal origin in amniotic fluid, obtained by routine amniocentesis from 25 pregnant women who smoked 10 or more cigarettes daily for 10 or more years and from 25 pregnant nonsmokers.

The women who participated in the study filled out questionnaires about their smoking habits and said they had not been drinking alcohol, coffee or tea during pregnancy.

The researchers said the association between maternal smoking and increased chromosomal instability in amniotic fluid cells was “expressed as chromosomal lesions (gaps and breaks) and structural chromosomal abnormalities.”

Specifically, they said, the proportion of structural chromosomal abnormalities among smokers was 12.1 percent, compared with 3.5 percent among nonsmokers. The scientists further concluded that the “chromosomal region most affected by tobacco” was a band commonly implicated in blood cancers, such as leukemia.

However, Mr. DeMarini said the Spanish data doesn’t confirm that smoking during pregnancy “could be setting up babies for an increased risk of leukemia,” because only five cases suggested this correlation.

“We still conclude that smoking is very bad for the fetus,” he said.