A risk factor is anything that increases a person's chance of developing cancer. Although risk factors often influence the development of cancer, most do not directly cause cancer. Some people with several risk factors never develop cancer, while others with no known risk factors do. However, knowing your risk factors and talking about them with your doctor may help you make more informed lifestyle and health care choices.

The following factors may raise a woman's risk of developing ovarian cancer:

Age. A woman’s risk of developing ovarian cancer increases with age. Women of all ages have a risk of ovarian cancer, but women over 50 are more likely to develop ovarian cancer (68% of women with ovarian cancer are older than 55 and 32% are younger than 55).

Family history. Ovarian cancer risk increases for women who have a first-degree relative (mother, daughter, or sister) who has had ovarian cancer. The risk increases when two or more first-degree relatives have had the disease.

Genetics. A mutation in the BRCA1 or BRCA2 gene is associated with an increased risk of ovarian cancer; there is also an increased risk of fallopian tube cancer and primary peritoneal (the membrane lining the abdomen) cancer, which are similar to ovarian cancer. Read more about BRCA1 and BRCA2 and hereditary breast and ovarian cancer. Women with hereditary non-polyposis colorectal cancer (HNPCC) also have an increased risk of developing ovarian cancer. Learn more about the genetics of ovarian cancer.

Ethnicity. Women of North American, Northern European, or Ashkenazi Jewish heritage have an increased risk of ovarian cancer.

Reproductive history. Women who have never had children, have unexplained infertility (the inability to bear children), have not taken birth control pills, or had their first child after the age of 30 have an increased risk of ovarian cancer. Also, women who started menstruation before age 12 and/or go through menopause later in life have an increased risk of ovarian cancer.

Hormones. Women who have taken estrogen-only hormone replacement therapy (HRT) after menopause have a higher risk of ovarian cancer.

Obesity.  Recent studies have shown that women who were obese in early adulthood are 50% more likely to develop ovarian cancer. Women who are obese are also more likely to die from the disease.

Behavioral and social factors.  Homosexual or bisexual women may have a higher risk of ovarian cancer than heterosexual women. This may be because lesbian women may be less likely to give birth, take oral contraceptives, or receive preventive screenings for fear of discrimination or insensitivity. Female-to-male transgendered and transsexual people may have a higher risk of ovarian cancer because of receiving hormones.

Prevention

Research has shown that certain factors may reduce a woman's risk of developing ovarian cancer:

• Taking birth control pills. Women who took oral contraceptives for three or more years are 30% to 50% less likely to develop ovarian cancer.
• Breastfeeding
• Pregnancy 

Women who have had a hysterectomy (the removal of the uterus and, sometimes, the cervix) or a tubal ligation (having the fallopian tubes tied surgically to prevent pregnancy) may have a lower risk of developing ovarian cancer.

Some women with strong family histories of ovarian cancer may consider a risk-reducing salpingo-oophorectomy. This is a preventive surgery to remove the fallopian tubes and ovaries, even if cancer is not diagnosed. This operation will significantly reduce, but not eliminate, the risk that a woman will develop ovarian or fallopian tube cancer. Women considering this surgery should talk with their doctor and a genetic counselor to fully understand the risks and side effects of this surgery compared with the risk of developing ovarian cancer.