Infertility itself, rather than the drugs that treat it, may cause ovarian cancer according to analysis.

For more than a decade, since fertility treatments became more widely available, there’s been controversy over whether drugs used in the treatment cycles make a woman more prone to ovarian cancer. A researchers at the Pittsburgh Graduate School of Public Health report on a review of several clinical trials and find that the drugs are not to blame.

However, there may well be a link between some causes of infertility – which cause women to take the drugs to treat it – and ovarian cancer. In particular, endometriosis and 'unknown cause' infertility seem to put a woman a risk. In endometriosis, cells from the uterine lining migrate to other parts of the pelvic cavity causing inflammation, pain and infertility. It’s possible the local inflammation plays a role in ovarian cancer.

The researchers looked at infertility and infertility drug use in 5,207 women with ovarian cancer and 7,705 healthy women in the US, Denmark, Canada and Australia. The study revealed that women who had been try to conceive for more than five years were 2.7 times more likely to develop ovarian cancer than those who became pregnant within a year. But those who took fertility drugs were no more likely to get cancer.

It’s important to realise that some causes of infertility did not increase ovarian cancer risk: ovulation or menstrual problems, ovarian cysts, blocked Fallopian tubes, uterine development problems and cervical problems. Looking at why endometriosis and unexplained infertility increase the risk could well lead to useful new insights on the biology of ovarian cancer.