Fertility treatment can double the long-term risk of invasive and low-grade ovarian cancers, a study has found.

Stimulating the ovaries of women undergoing in vitro fertilisation increased the chances of patients being diagnosed with ovarian cancer 15 years later.

Overall, ovarian cancer rates were doubled by the treatment which forces the ovaries to produce extra eggs.

The main impact was on non-fatal slow-growing tumours. The risk of developing this condition, known as “borderline ovarian cancer”, was raised four-fold.

Although not considered dangerous, borderline ovarian cancer still requires extensive surgery.

Scientists analysed data on more than 19,146 subfertile women who had received at least one ovarian stimulation treatment, and 6,006 subfertile women who did not undergo IVF.

Of 61 women who had ovarian malignancies in the IVF treatment group, 31 had borderline ovarian cancer and 30 had invasive ovarian cancer.

Study leader Flora van Leeuwen, professor from The Netherlands Cancer Institute in Amsterdam, said: “Our data clearly show that ovarian stimulation for IVF is associated with an increased risk of borderline ovarian tumours and this risk remains elevated up to more than 15 years after the first cycle of treatment.”

The risk of potentially deadly invasive ovarian cancer was also raised, but not by a level that was statistically significant.

Prof. van Leeuwen said this result may be influenced by how many children, if any, a woman receiving IVF treatment had already given birth to. She stressed that the individual risk of developing either invasive or borderline ovarian cancer was “very low”.

Ovarian cancer is the fifth most common cancer among UK women, with more than 6,500 cases diagnosed each year.

It has been called the “silent killer” because often the disease is not detected until an advanced and lethal stage.

Each year around 4,400 British women die from ovarian cancer, a large proportion of those who are diagnosed.