It is the first hard evidence to suggest that passive smoking can cause the same type of genetic damage in unborn infants as that found in adult smokers with cancer.
The implications are that an untold number of unborn children are being put at risk as a result of their mothers being exposed to passive smoking while pregnant. Scientists say the results show there is a need for even tougher rules on smoking in public places.
A study in the United States of 12 newborn babies born to women who were exposed to passive smoking, and 12 infants whose mothers were not subjected to other people's cigarettes, is the first to demonstrate that secondary tobacco smoke causes genetic mutations in the womb. The researchers, led by Barry Finette, a paediatrician at the University of Vermont in Burlington, analysed blood samples taken from the babies at birth for mutations in a gene that is linked with childhood cancers.
"Some studies suggest that children whose mothers smoked during their pregnancy are not at an increased risk for developing cancer as a child,'' the researchers report in the journal Nature Medicine.
"In contrast, there is accumulating evidence that maternal exposure to passive smoke, as well as a history of paternal cigarette smoke exposure in the absence of maternal cigarette smoking, is correlated with an increased risk of childhood cancer, especially leukaemias and lymphomas in children less than five years of age."
The research on pregnant women exposed to passive smoking is the first clear evidence of a biological link between tobacco and potentially malignant changes in children, the researchers said.
The study found mutations in the white blood cells of the babies but the scientists warned that there could be other genetic transformations that they might have missed.
"Given our small sample size, there may well be other differences that we were unable to detect. However, the statistical significance of the differences we found are as valid as those from a much larger study, provided [our] sample is representative," they said.
Another study, published last August, on the effects of tobacco smoke on pregnant women found significantly high levels of cancer-causing substance in the first urine samples of newborn infants.
The latest research strengthens the case for increasing the protection of pregnant women against smokers, says Dr Gabriella Sozzi, a cancer specialist at Italy's National Cancer Institute in Milan, in an editorial in the journal.
"This study provides incontrovertible genetic evidence of the devastating effects of tobacco smoke particularly on the young, who suffer a greater risk from environmental toxicants ... not only because of their small size but also because of their physiological immaturity."
No other environmental factor, whether to do with diet, lifestyle or pollution, has such a pronounced effect on the risk of developing cancer as tobacco smoke, Dr Sozzi said.Reuse content