IVF (in vitro fertilisation) may increase the risk of ovarian cancer by as much as a third, researchers fear. Women having the treatment should be regularly screened.
The procedure involves hormone drugs, and these may be responsible for the increased risk, say researchers from University College London, who analysed the outcome of more than 250,000 IVF treatments.
Although there was no difference in rates of breast and uterine cancers in the women compared to those who didn't have IVF, there was a 30 per cent increase in rates of ovarian cancer.
The researchers aren't sure whether the treatment is the cause, but say that women should be warned of the possibility and regularly screened if they do proceed with the treatment.
Their suggestion is controversial. IVF was for a long time thought to cause cancer until it was given a clean bill of health by a major Cochrane review in 2013.
If the risk exists, it is still low, however; 15 in every 10,000 women undergoing IVF developed ovarian cancer compared with 11 per 10,000 in the general population.
(Source: Proceedings of the American Society for Reproductive Medicine annual conference, October 20, 2015)