Ovarian cancer happens when cells in the ovaries grow and spread, producing a lump of tissue called a tumour.
It's not clear why this happens. But there are factors that may increase your risk of getting ovarian cancer.
The risk of ovarian cancer increases as you get older. Most cases happen after menopause.
About 8 in every 10 women diagnosed with ovarian cancer are over 50. But some rare types of ovarian cancer can happen in younger women.
Family history and genes
You're more likely to get ovarian cancer if you have a history of it in your family. For example, if your sister or mother has had it.
Sometimes this may be because you've inherited a faulty version of a gene called BRCA1 or BRCA2. These increase your risk of developing both ovarian and breast cancer.
But having relatives with ovarian cancer does not mean you definitely have a faulty gene. Only around 1 in every 10 ovarian cancers is caused by 1 of these genes.
Talk to your GP if you're worried that your family history might mean you're at a higher risk of ovarian cancer.
Hormone replacement therapy (HRT)
Taking hormone replacement therapy (HRT) may increase your risk of ovarian cancer. But the risk is very small.
Any increased risk of ovarian cancer is thought to reduce after you stop taking HRT.
If you have endometriosis, you may be slightly more at risk of developing ovarian cancer.
Read more about endometriosis
Other things that may increase your risk of ovarian cancer.
Being overweight or obese
Stopping smoking may help to reduce your risk of ovarian cancer and many other serious health problems.
Exposure to asbestos
A material that was used in buildings for insulation, flooring and roofing in the past, but is no longer used.
Using talcum powder
Some research suggests that using talcum powder on your genitals could increase your risk of ovarian cancer. But the evidence is not clear and the risk is likely to be very small.