Pregnant women subjected to passive smoking give birth to babies with an increased, lifelong susceptibility to cancer, research reveals.
Passive smoking causes the same type of genetic damage in unborn infants as that found in adult smokers with cancerous tumors.
Researchers said the abnormalities in newborns were indistinguishable from those found in babies of mothers who were active smokers.
And they may affect survival, birth weight and lifelong susceptibility to diseases like cancer, according to the study published online in the Open Paediatric Medicine Journal.
Dr Stephen Grant and colleagues at the University of Pittsburgh in the U.S. found a smoke-induced mutation in an oncogene, a gene which transforms normal cells into cancerous tumors.
The mutation was the same level and type in newborns of mothers who were active smokers as those in babies born to non-smoking mothers exposed to tobacco smoke.
The mutations were also discernible in newborns of women who had stopped smoking during their pregnancies, but who did not actively avoid second-hand smoke.
The study confirms previous research in which Dr Grant discovered evidence of genetic abnormalities in babies whose mothers were exposed to environmental tobacco smoke.
There is also evidence that maternal exposure to passive smoke, as well as a history of paternal cigarette smoke exposure, is linked with an increased risk of childhood cancer, especially leukaemias and lymphomas in children under five.
Dr Grant said: 'These findings back up our previous conclusion that passive, or secondary, smoke causes permanent genetic damage in newborns that is very similar to the damage caused by active smoking.
'By using a different laboratory test, we were able to pick up a completely distinct yet equally important type of genetic mutation that is likely to persist throughout a child's lifetime.
'Pregnant women should not only stop smoking, but be aware of their exposure to tobacco smoke from other family members, work and social situations.'Source