TUESDAY, March 8, 2005 (HealthDayNews) -- Mothers who smoke during pregnancy could be causing chromosomal abnormalities in fetal cells that may increase risks for both childhood and adult leukemia, a new study claims.

That smoking has adverse effects both during and after pregnancy is well known. Smoking has been linked to health problems such as infertility, blood clotting, birth complications and low birth weight. Until now, however, the evidence that smoking can damage an infant's DNA has not been shown directly.

But the results of a new study suggest that smoking during pregnancy does cause DNA damage. The report appears in the March 9 issue of the Journal of the American Medical Association.

"In mothers who smoke during pregnancy, there is an increase of chromosomal lesions in the cells of the fetus," said co-author Dr. Josep Egozcue, a professor of medicine at the Universitat Autonoma de Barcelona in Bellaterra, Spain.

However, editorialists commenting in the journal say the findings are far from conclusive.

In their study, Egozcue and his colleagues interviewed 800 pregnant women to find 25 who reported smoking 10 or more cigarettes a day for 10 years or more, and 25 who never smoked. The research team took samples of amniotic fluid during routine amniocentesis.

Compared with nonsmokers, the researchers found the fetuses of women who smoked during pregnancy had more chromosomal abnormalities. This was especially true for chromosomal regions involved in forming blood cells.

The relationship of chromosomal damage to leukemia is not direct, Egozcue explained. "It is a possibility, because the most frequent lesion in the smoker group was a lesion in the region of chromosome 11, which is found in a high percentage of children and adults with different types of leukemia," Egozcue said.

"This is not a direct relationship," Egozcue stressed. "We don't want to alarm people, because otherwise all mothers who smoked during pregnancy would go crazy."

But given these findings, Egozcue said, smoking during pregnancy may be even more dangerous than has been thought. "We need to convince women not to smoke at all if possible, especially not to smoke during pregnancy."

The Spanish study is very important, write journal editorialists David M. DeMarini and R. Julian Preston, because this type of investigation has never been done before. However, according to DeMarini, the study does contain flaws.

"For one thing, the study is lacking an independent assessment of the smoking," DeMarini said. Since smoking habits were self-reported by the women, there is no way to check to be sure their reports are accurate, he noted.

Another problem DeMarini sees is that the analysis of chromosomal damage is less than convincing. "The data are not wildly strong," DeMarini said. "They are suggestive, but not highly convincing."

DeMarini, a genetic toxicologist with the U.S. Environmental Protection Agency, thinks that some of the DNA abnormalities Egozcue's group found could be random artifacts. "Without a larger population and a bigger study, you are on the edge of statistical probability as to whether they found an increase in chromosome mutations," he said.

In addition, DeMarini believes the data suggesting a possible increased risk of leukemia remains weak. "The numbers are so limited, it's just very tenuous to make that argument," he said. "The data, although interesting and perhaps suggestive, by no means demonstrate a real increased risk for leukemia for the children of smokers."

More information

The American Lung Association can tell you more about smoking and pregnancy.

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