Future smokers may be programmed in the womb to take up the habit later in life, research published on Tuesday said.
Scientists in Australia have discovered that children of women who smoked during pregnancy were more likely to become smokers than other youngsters.
They suggest nicotine from cigarettes passes through the placenta and may act directly on the developing brain of the unborn child.
"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," Dr Abdullah Al Mamun, of the University of Queensland, said in the study published in the journal Tobacco Control.
The researchers studied the smoking patterns of more than 3,000 mothers and their children who took part in a long-term study in Brisbane, Australia.
Children of the 1,000 women who had smoked during pregnancy were three times more likely to start smoking by the age of 14 and twice as likely afterwards compared to other children.
The researchers said their results were consistent with findings of earlier studies into the impact of smoking during pregnancy on the child.
The charity ASH (Action on Smoking and Health) welcomed the research, saying it stresses the importance of health education and of dissuading all women of child-bearing age from smoking.
"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," a spokesperson said.
In addition to influencing the developing fetus, researchers have also shown that heavy smokers have lower odds of becoming pregnant through IVF (in-vitro fertilization), even with a donated egg, because smoking makes their womb less receptive to the embryo and reduces the chances it will implant.
Male smokers are also more likely to suffer from impotence.
