MOTHERS are 40 per cent less likely to develop ovarian cancer than women without children, a University of Oxford study has found.

The research, to be presented today at the National Cancer Research Institute (NCRI) cancer conference in Liverpool, found a 40 per cent risk reduction for endometrioid and clear cell tumours, two of the four most common types of ovarian cancer.

Experts already knew that children cut the risk of the disease, but research wasn’t specified to different types of ovarian cancer until now.  

The study found a 20 per cent risk reduction in any type of ovarian cancer in women with one child. The risk decreases by a further 8 per cent for every extra child.

8,000 women with ovarian cancer took part in the study, led by Cancer Research-funded scientist Dr Kezia Gaitskell, from the University of Oxford.

She said: "We think that the significant reduction in risk among women with one child compared to women without children is likely to be related to infertility, as there are some conditions - such as endometriosis - that may make it harder for a woman to become pregnant, and which may also increase her risk of these specific types of ovarian cancer.

"Our results are really interesting, because they show that the associations with known risk factors for ovarian cancer, such as childbirth and fertility, vary between the different tumour types."

Researchers also discovered a 20% reduced risk of ovarian cancer for women who had been sterilised.  

Annwen Jones, chief executive of Target Ovarian Cancer, said: "This research could also help us to develop new, more effective, treatments for ovarian cancer."

Around 7,100 women are diagnosed with ovarian cancer in the UK each year. It is the fifth most common cancer in women, after breast, lung, bowel and womb cancer.