Doctors do not know what causes cancer to start in the ovary. But there are some risk factors that may increase the chances of it developing.

Doctors know less about the risk factors for fallopian tube and primary peritoneal cancers because these cancers are less common. But doctors think they are generally the same as the risk factors for epithelial ovarian cancer. This is the most common type of ovarian cancer.

Having a risk factor does not mean you will get cancer. And if you do not have any risk factors, this does not mean you will not get cancer.

Age

More than half (50%) of ovarian cancers develop in women after the age of 65. These cancers are rare under the age of 30. The risk of ovarian cancer increases with age.

Hormonal factors

Doctors think the number of times an ovary releases an egg (ovulates) may be linked to ovarian cancer risk. This is because there is evidence that having children, breastfeeding, and taking the contraceptive pill reduces the risk of ovarian cancer.

Hormone replacement therapy (HRT)

Taking HRT, which uses oestrogen, progesterone or both, after the menopause slightly increases the risk of ovarian cancer. About 4 in 100 (4%) of cases may be linked to taking HRT. But doctors think this is only for serous and endometrioid ovarian cancers.

Breast cancer

If you have had breast cancer, you may be more likely to develop ovarian cancer. This may be because these cancer types share the same risk factors. But doctors think it may be because both cancers can be caused by the same cancer genes.

Other conditions

Some other conditions can increase your risk of developing ovarian cancer.

• Diabetes: Having diabetes may increase the risk of developing ovarian cancer.
• Endometriosis: Endometriosis is a non-cancerous condition. With this condition, cells similar to the cells that line the womb are found in areas outside the womb. Some people worry about a link between endometriosis and developing ovarian cancer. But studies show that having endometriosis only slightly increases the risk of endometrioid and clear cell ovarian cancers. These types of ovarian cancer are often diagnosed earlier when they are easier to treat successfully.

Lifestyle factors

There are also some lifestyle factors that can increase your risk of developing ovarian cancer.

Weight

Being overweight (obese) may increase the risk of some ovarian cancers.

Smoking

Smoking cigarettes may slightly increase the risk of developing a less common type of ovarian cancer called mucinous cancer. But it does not affect your risk of epithelial ovarian cancer which is the most common type.

Family history of ovarian cancer

Having a family history of ovarian cancer can increase your risk of developing it. If your mother or sister has had ovarian cancer, your risk may be up to 3 times higher. If they were diagnosed at a young age, your risk may be higher.

Your GP can also give you information and support. If they think your family might have an increased risk of ovarian cancer, they may arrange for you to see a genetics specialist. We have more information for people who are worried about a worried about a family history of ovarian cancer.

Inherited genetic conditions

Around 5 to 15 out of 100 (5 to 15%) of ovarian cancers are thought to be caused by a change (mutation) in a gene that is passed on in the family. Genes contain our genetic information, which is passed on from our parents. Some cancers, such as ovarian, breast, bowel and womb cancers, may affect several people in the same family. They may develop at a younger age.

BRCA1 and BRCA2

The most commonly affected genes are called BRCA1 and BRCA2. If you have a mutation in one of these genes, you may have a higher risk of ovarian, fallopian tube, primary peritoneal and some other types of cancer.

If you have a mutation in the BRCA1 gene, your risk of developing ovarian cancer is up to 65% higher. With BRCA2, it is up to 35% higher. Families from all ethnic backgrounds can be affected by a gene mutation linked to cancer. But families from an Ashkenazi Jewish background have a particularly high risk of having BRCA1 or BRCA2 mutations.

Rare genetic conditions

Lynch syndrome and Peutz-Jeghers syndrome are both rare genetic conditions that affect some families. They can increase the risk of some cancers, including ovarian cancer. 

Click here to view our Ovarian Cancer Health Articles.