Ovarian cancer happens when cells in the ovaries grow and multiply uncontrollably, producing a lump of tissue called a tumour.
It's not clear exactly why this happens, but there are factors which may increase your risk of getting ovarian cancer.
The risk of ovarian cancer increases as you get older, with most cases happening after the 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.
You're more likely to get ovarian cancer if you have a history of it in your family, particularly if a close relative (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 thought to be caused by 1 of these genes.
The charity Ovarian Cancer Action has a tool to help you check whether your family history puts you at risk of ovarian cancer.
Speak to a GP if you're worried that your family history might mean you're at a higher risk of ovarian cancer. They may refer you to see a genetic counsellor, who may suggest having a test to check for faulty genes.
Read more about genetic testing for cancer risk genes.
It has been suggested that taking hormone replacement therapy (HRT) may increase your risk of ovarian cancer. But studies looking at this have so far had conflicting results.
It's thought that if there is any increase in cases of ovarian cancer in women taking HRT, the risk is very small.
Any increased risk of ovarian cancer is thought to decrease after you stop taking HRT.
Research has shown that women with endometriosis may be more likely to develop ovarian cancer.
In endometriosis, the cells that usually line the womb grow elsewhere in the body, such as in the ovaries or tummy.
These cells still behave as if they were in the womb, including bleeding during periods. But as there's no way for the bleeding to leave the body, it becomes trapped and causes pain in the affected area.
Other things that may increase your risk of ovarian cancer include:
- being overweight or obese – losing weight through regular exercise and a healthy diet may help to lower your risk
- smoking – stopping smoking may help to reduce your risk of ovarian cancer and many other serious health problems
- exposure to asbestos – a whitish material that was used in buildings for insulation, flooring and roofing in the past, but is no longer used
- using talcum powder – some research has suggested that using talcum powder between your legs could increase your risk of ovarian cancer, but the evidence for this is inconsistent and any increase in risk is likely to be very small