We do not know what causes cancer to start in the ovary, fallopian tube or peritoneum. But we know some of the risk factors that may increase the chances of it developing.

We know less about the risk factors for fallopian tube and primary peritoneal cancer because these cancers are less common. But they are likely to be similar to the risk factors for ovarian cancer.

Having a risk factor does not mean you will definitely get cancer. Equally, if you don’t have any risk factors, it does not mean you will not get cancer.

Age

These cancers are rare in people under the age of 30. The risk increases with age. More than half of ovarian cancers occur in people over the age of 65.

Hormonal Factors

Doctors think the number of times an ovary releases an egg (ovulates) may be linked to ovarian cancer risk. These cancers are more common in people who have ovulated more times. For example, if you:

• have never given birth
• give birth for the first time after the age of 35
• start their periods young
• have a later menopause.

Factors that reduce ovulation may help lower the risk of ovarian cancer. For example, taking the contraceptive pill, having more pregnancies and breastfeeding.

Hormone replacement therapy (HRT)

Taking HRT after the menopause slightly increases the risk of developing ovarian cancer. About 1% of cases may be linked to taking HRT.

Medical Conditions

Breast cancer

If you have had breast cancer you may be more likely to develop ovarian cancer. This may be because these cancers have some risk factors in common.

Endometriosis

Endometriosis is a condition where the lining of the womb grows outside the womb. Having this condition slightly increases the risk of ovarian cancer.

Diabetes

Having diabetes may slightly increase the risk of developing ovarian cancer. We have more information about going through cancer treatment if you have diabetes.

Lifestyle Factors

Smoking

Smoking cigarettes increases your risk of a less common type of ovarian cancer called mucinous cancer. It does not affect your risk of the most common type of ovarian cancer.

Weight and height

There is limited evidence that being overweight, obese or taller may increase the risk of ovarian cancer.

Family history

If you have a family history of ovarian cancer, you may have a higher risk of developing it yourself. Your risk may be about 3 times higher if you have 1 close relative with ovarian cancer. If you have 2 or more close relatives with ovarian cancer or certain other types of cancer, your risk may be higher than this.

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

Inherited genetic conditions

All cells in the body contain genes. These genes are the instructions your cells need to work. Genes affect the way your body grows, functions and looks. Sometimes a gene is damaged or develops a fault (mutation). Changes like this can be linked to a higher risk of certain health problems.

Genes are passed from parent to child. Half of the genes in your cells are identical to some of your father’s genes and half are identical to some of your mother’s. This means gene mutations can be passed on from parent to child.

A small number of cancers that start in the ovaries, fallopian tubes or peritoneum are linked to a gene mutation. If a family has a gene mutation linked to ovarian cancer, there may be a pattern of cancer in that family. Several people in the family may be affected by ovarian cancer or related cancers, such as breast, bowel or womb cancer. They may also develop these types of cancer at an unusually young age.

BRCA1 and BRCA2

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

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.

Lynch syndrome

Lynch syndrome is a rare genetic condition that affects some families. It increases the risk of several types of cancer, including ovarian cancer.