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Risk factors are what doctors call things that increase your chance of getting a disease.

Most women who get ovarian cancer don't have any risk factors.^{1 2 3 4 5} And even if you have a risk factor for this cancer, it doesn't mean you'll get it for sure. Most people with risk factors don't get ovarian cancer.

Here's what we know about factors that affect your risk of ovarian cancer. Some of them increase your risk, while others decrease it.

Having someone in your family who's had ovarian cancer is the strongest risk factor.

• The average woman in the United States has a 1 in 60 chance of getting ovarian cancer.
• But if you have one close family member (such as a sister or mother) who's had it, your chance of getting it is about 1 in 20.⁶
• If you have two or three close family members who've had ovarian cancer, your chance of getting it is about 1 in 14.⁶
• If you have other family members (aunts, cousins, grandmothers) with ovarian cancer, your risk may be higher than average, but less than if a close family member has it.⁷
• If any of your close family members have had breast cancer or colon cancer, you may also be at higher risk of getting ovarian cancer.⁷ (To learn more about these conditions, see our sections on breast cancer and colon cancer.)

For more information about what you can do if ovarian cancer runs in your family, see Ovarian cancer and your family.

Getting older increases your risk. Most women who get ovarian cancer are older than 50, but younger women can get it, too.⁸

If you've never had children or been pregnant, you're more likely to get ovarian cancer. Your risk of getting it is about 1 in 50.⁹ Breaks from your menstrual cycle seem to protect you, but we don't know why.

If you've had breast cancer or colon cancer, or cancer of the uterus (womb) or rectum, you may be more likely to get ovarian cancer.¹⁰

Doctors aren't sure if taking fertility drugs to help you get pregnant affects your chance of getting ovarian cancer. Some studies say that it increases your risk, but others say that it doesn't.^{1 5} If you're taking these drugs and you're worried, talk to your doctor.

It's not clear whether using talcum powder around your genitals increases your risk of ovarian cancer. There's some evidence that it might, but we need more research to say for sure.¹¹

The more children you have, the less likely you are to get ovarian cancer.¹⁰ Breaks from your menstrual cycle seem to protect you, but we don't know why. Your cycle also often stops when you breastfeed, so the longer you do this, the less likely you are to get ovarian cancer.

If you take birth control pills, you're less likely to get ovarian cancer. All the research is on older types of pills, which had more of the hormone estrogen in them. But it's probably also true of birth control pills used today, which have much less estrogen in them.

Taking the pill for five years cuts your chance of getting ovarian cancer by about half.^{11 12 13 14} But if you take the pill for longer than five years, your risk won't continue to get lower. So whether you take it for five years or 10 years, you have the same protection.

If you have a hysterectomy (an operation to remove your womb), your ovaries may be taken out at the same time. You can also have an operation to take out just your ovaries.

Having your ovaries taken out greatly reduces your chance of getting ovarian cancer.¹⁵ But removing your ovaries doesn't take away all the risk of getting this type of cancer. This is because there may be some cells left behind after surgery. These cells could turn into cancer in the place where your ovaries used to be. They could also spread to other areas. But the chance of these things happening is very small.¹⁵

If you have your ovaries taken out, there are some things you should know.

• You can't get pregnant naturally after having your ovaries removed. But you may be able to get pregnant by having fertility treatments.
• If you haven't reached menopause yet, having your ovaries taken out may cause symptoms of menopause, such as hot flashes, sweating at night and a dry vagina, as well as thinning of your bones (called osteoporosis). You can take treatments to ease some of these problems. For more information, see our section on menopause.

If you're thinking about this surgery because ovarian cancer runs in your family, see Ovarian cancer and your family.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.