Male cancer survivors may be slightly more likely than other men to father children with major congenital birth abnormalities, according to a new study.

The results showed that 3.7 percent of children of men who'd survived cancer were born with the abnormalities, while 3.2 percent of children of men without any history of cancer were born with them.

The use of reproductive technologies, such as in vitro fertilization , did not increase in the risk of malformations compared with natural conception, the researchers said.

And the babies of male cancer survivors were no more likely to be born early or with a low birth weight than the babies of other men, the study found.

The researchers studied 1.8 million children born in Sweden and Denmark between 1994 and 2004. Of these, 8,670 children were born to men who'd survived cancer.

A 2008 study in the journal Human Reproduction also found an increased risk in congenital abnormalities among the first-born children of male cancer survivors. However, several other studies have shown no increased risk, the researchers said.

The new study was larger than the previous ones with contradictory findings, and so was better able to detect the small, but significant, increase in risk, the researchers said.

The increasing number of male cancer survivors has given rise to concerns about the health of their offspring, the researchers said. Some cancer therapies may cause mutations that could be passed on to children.

However, the researchers also said that their findings suggested that the increased risk of congenital abnormalities may be related more to the cancer itself than to treatments for the disease the men may have undergone.

For example, men with a cancer called testicular seminoma, who would have likely been treated with radiation, were no more likely than men with no history of cancer to father children with congenital abnormalities. However, among men with skin cancer , who would have likely been treated with a surgical removal of a small area of skin, the researchers found an almost 40 percent increase in the risk of fathering a child with congenital abnormalities.

The findings are "overall quite reassuring," wrote Lisa B. Signorello, of the International Epidemiology Institute and Vanderbilt University, in an editorial that accompanied the study. Still, the results are incomplete, because of limited data available and the fact that the study included only male cancer survivors.

It's also possible, Signorello wrote, that parents who've had a serious, sometimes inherited disease, may be more likely to be more watchful of signs that something is wrong in their children.

The study was published online today (Feb. 8) in the Journal of the National Cancer Institute.

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