In addition, the study authors looked at over 1.7 million children who were born during the same time period to men with no history of cancer, of which almost 26,000 were conceived using ART.
Babies of male cancer survivors were 17 percent more likely to have a "major" congenital abnormality compared to babies born to healthy fathers, the investigators found.
However, the overall risk was very low: in absolute terms, it was only 3.7 percent among children of cancer survivors, compared to 3.2 percent for offspring of males without any history of cancer, regardless of mode of conception.
The risk seemed to be highest among men who had had skin, eye and central nervous system cancers, but there was no increased risk with testicular cancer, the researchers noted.
Children conceived using ART also had a 20 percent increased risk of major congenital abnormalities compared to children conceived normally, although the method of conception didn't affect the association between paternal history of cancer and birth defect risk.
There was also a slightly higher risk among men who conceived after the age of 18 and possibly for men who conceived within two years after their cancer diagnosis, but these were not "statistically significant," said Giwercman.
Though not proven yet, the authors indicated that the results suggest that the malignancy itself, as opposed to the treatments, is probably responsible for the abnormalities.
"We cannot say this for sure . . . however our preliminary results indicate that this is rather the cancer diagnosis per se and not the treatment by radio- and/or chemotherapy, which is the cause of slight increase in the malformation risk among the children," said Giwercman.
Besides the very low absolute risk of birth defects, the finding
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