Each year, about 6600 women in the UK are diagnosed with ovarian cancer. The causes are not yet completely understood. The risk of developing ovarian cancer is very low in young women and increases as women get older. Over eight out of ten (85%) ovarian cancers occur in women over the age of 50. Most ovarian cancers occur in women who have had their menopause.

Some factors are known to affect a woman’s chance of developing ovarian cancer – they may increase the risk or decrease it. These are described below.

• Women who have not had children are slightly more likely to develop ovarian cancer than women who have, although the risk is still very low. Having two or more children may provide more protection than just one.
• Breast feeding your children may slightly decrease your risk.
• Starting your periods early or having a late menopause slightly increases your risk of ovarian cancer.
• Women who take the contraceptive pill are less likely to develop ovarian cancer.
• Using oestrogen-only hormone replacement therapy (HRT) can slightly increase the risk. When HRT is stopped the risk of ovarian cancer gradually reduces to the same level as women who haven’t taken HRT.

Research has shown that infertility treatment may slightly increase the risk of developing ovarian cancer. However, other research doesn’t support this.

• Having endometriosis may increase your risk of ovarian cancer.

• Being overweight may increase your risk of developing ovarian cancer.
• Eating a diet high in animal fats and low in fresh fruit and vegetables may increase your risk.

• About 5–10 in 100 (5–10%) ovarian cancers are caused by an inherited faulty gene in the family.
• Women who have had breast cancer have an increased risk of ovarian cancer. This is because breast and ovarian cancer can be caused by the same faulty genes.

If any of the following are present in one side of your family, it is possible that there may be an inherited faulty gene:

• Ovarian cancer in at least two close relatives (mother, sisters or daughters).
• One close relative with ovarian cancer and one close relative with breast cancer diagnosed when they were under the age of 50 (or both cancers in the same person).
• Ovarian cancer in one close relative and breast cancer in two family members diagnosed when they were under the age of 60.
• Three close relatives with colon (bowel) or womb (endometrial) cancer, and one relative with ovarian cancer.

Having one elderly relative with ovarian cancer doesn’t necessarily increase your risk of ovarian cancer.

Women who are worried that they may have an increased risk of developing ovarian cancer, because of cancer in their family, can be referred to a genetic counselling clinic. Contact your GP or our information service for more details about genetic counselling clinics. The clinics are based in hospitals and you will be seen by a genetics specialist who can check your family history to see whether you are likely to be at increased risk.

If two or more of your close relatives have had ovarian cancer you may want to consider having testing (screening) for ovarian cancer. However, it is not yet known how effective screening is at detecting ovarian cancer (screening).