It is unlikely that the drug thalidomide, associated with limb defects, would cause a genetic mutation which passed on similar defects to victims' children, according to the director of the National Centre of Medical Genetics in Crumlin, Dublin. Prof Andrew Green, also professor of medical genetics in UCD and a genetics consultant at Our Lady's Hospital for Sick Children in Crumlin, was responding to a report that an English family was seeking compensation for their daughter, claiming she was the second generation affected by the drug.
In the 1960s thalidomide was widely prescribed to women suffering from morning sickness in pregnancy. The drug caused limb and other defects in their babies, many of whom died young. At least nine of about 300 children born to thalidomide victims have had similar though milder limb defects, a higher proportion than among the population as a whole.
However, Prof Green does not think this is a result of the drug. "There is no question that thalidomide causes damage to developing limbs," he told The Irish Times, "but that is not genetic damage. It was not a mutagenic defect - the drug affected cells rather than genes. It is very unlikely that it has a separate effect on a particular gene."
Elements which affected genes did so at random and, as there were about 100,000 genes, it was unlikely the drug would hit precisely the gene which determines limb development.
Birth defects happened because pregnant women took thalidomide when foetal limbs were developing. Genes can be damaged long before conception and genetic defects are usually present at the moment of conception, before the woman knows she is pregnant and before she would have been prescribed thalidomide.
So why do thalidomide sufferers have a higher proportion of children with limb defects? "Some of those who were awarded money in the 1960s, and whose mothers took thalidomide, might quite possibly have had independent genetic disorders which caused limb defects. There are hereditary forms of limb defects, which usually start at the moment of conception." These could be showing up in the next generation, he said.
"I am quite concerned that people who have thalidomide defects would be worried unnecessarily about their children."