Nicotine crossing the placenta and affecting the brain of the unborn child may explain why children of women who smoke during pregnancy tend to become smokers themselves, Reuters reported Nov. 27.

A study of 3,000 mothers and their children found that children of the 1,000 women who smoked during pregnancy were three times as likely to become smokers themselves by age 14. They also were twice as likely to become smokers after age 14.

"Our findings suggest a direct effect of maternal smoking during pregnancy on young adults' development of regular smoking, and provide yet another incentive to persuade pregnant women not to smoke and to discourage young women from ever taking it up," said researcher Abdullah Al Mamun of the University of Queensland, Australia.

"It does seem there is a pharmacological influence on the developing fetus which underlines yet again the importance of women stopping smoking as soon as they know they are pregnant," added a spokesperson for the group Action on Smoking and Health (ASH).

The study was published in the December 2006 issue of the journal Tobacco Control.