Scientists have found no significant link between the use of fertility drugs and the risk of breast, ovarian and uterine (womb) cancer.

According to the findings, there is ‘little evidence' that fertility hormones used to stimulate the ovaries increase the risk of these cancers.

Fertility drugs are known to increase levels of the female hormones, oestradiol and progesterone, both of which have been linked to cancer of the breast, ovaries and uterus.

US scientists decided to look into this further. They monitored over 12,000 women who had been treated for fertility problems between 1965 and 1988. The women were followed up until 2010.

"Despite the biologic plausibility, results of studies of fertility drugs and breast and gynecological cancers present a mixed picture, with some showing increases in risk, others decreases, and still others showing no substantial associations. However, most of these studies had small numbers with relatively short follow-up periods, and were unable to control for other cancer predictors which could independently affect cancer risk," the scientists said.

During the 30-year follow-up period, 749 women developed breast cancer, 119 developed uterus cancer and 85 developed ovarian cancer.

The scientists found ‘little evidence' of any links between fertility drugs and these diseases. For example, around 40% of the women had used the drug, clomiphene citrate (Clomid), to help stimulate ovulation. However, use of this drug was not associated with any increased risk of breast cancer unless the women had used it in 12 or more treatment cycles.

Furthermore, use of this drug was not associated with an increased risk of uterine or ovarian cancers, even if used multiple times.

Meanwhile, one in 10 of the participants had been treated with gonadotrophins - also used to stimulate ovulation - and this did not appear to increase the risk of these cancers unless the women never went on to have any children.

According to Dr Humberto Scoccia of the University of Illinois, these findings do not suggest ‘a strong relationship' between the use of fertility drugs and these cancers.

He described them as ‘generally reassuring', but acknowledged that this area needs to be constantly monitored.

Dr Scoccia presented these findings at the 30th Annual Meeting of the of the European Society of Human Reproduction and Embryology (ESHRE) in Munich, Germany.