What we know and don't know about ovarian cancer causes

Ovarian cancer does not have a single cause. Instead, it develops when cells in or around the ovaries begin to grow abnormally, and this happens because of a combination of factors—some you inherit, some tied to your age or reproductive history, and some that remain unexplained even after diagnosis. Researchers have identified clear risk factors that make ovarian cancer more likely, but having a risk factor does not mean you will develop the disease, and many people without any known risk factors do develop it.

Understanding what increases your risk matters because some factors—like family history or certain genetic mutations—can change how you and your doctor approach screening or prevention. Other factors, like age or past pregnancies, are simply part of your medical story and cannot be changed. This guide explains what research has found so far about what leads to ovarian cancer.

Key Takeaways

  • Age is the strongest risk factor; most ovarian cancers occur in people over 50, though younger people can develop it.
  • Inherited mutations in the BRCA1 and BRCA2 genes significantly raise ovarian cancer risk and are worth testing for if you have a family history of cancer.
  • A personal or family history of breast, colon, or ovarian cancer increases your risk because these cancers share genetic links.
  • Reproductive factors like never being pregnant, late menopause, or long-term hormone therapy use are associated with higher risk.
  • Obesity, smoking, and endometriosis are linked to ovarian cancer, though the exact mechanisms are still being studied.

Age and why ovarian cancer is more common in older people

Age is the strongest known risk factor for ovarian cancer. Most cases occur in people aged 50 and older, with the average age at diagnosis around 63. This pattern reflects how cancer develops in general: cells accumulate mutations over decades, and the longer cells are exposed to potential damage, the more likely one will become cancerous.

Younger people do develop ovarian cancer, but it is less common. When it occurs before age 40, inherited genetic factors or family history are more likely to be involved. If you have a family history of ovarian or breast cancer, your risk begins earlier than it does for people without that history, which is why genetic testing and earlier screening conversations may matter for you.

BRCA1 and BRCA2 mutations and inherited cancer risk

BRCA1 and BRCA2 are genes that normally help repair damaged DNA. When these genes carry mutations passed down through families, they cannot do that job properly, and cells are more likely to become cancerous. People who inherit a BRCA1 mutation have roughly a 35 to 70 percent lifetime risk of developing ovarian cancer, depending on the specific mutation and other factors. BRCA2 mutations carry a lower but still significant risk, around 10 to 30 percent.

These mutations are not common in the general population, but they run in families and are more frequent in certain ancestry groups, particularly Ashkenazi Jewish populations. If you have a parent, sibling, or child with a BRCA mutation, or if multiple relatives on one side of your family have had breast, ovarian, or pancreatic cancer, genetic testing can tell you whether you carry a mutation. Testing is a blood test, and results can guide decisions about screening, prevention, or surgery.

Other inherited mutations in genes like PALB2, RAD51C, and BRIP1 also raise ovarian cancer risk, though less dramatically than BRCA mutations. Genetic counseling before and after testing helps you understand what results mean for your health and your family.

Family history and personal cancer history

If a close relative—parent, sibling, or child—has had ovarian cancer, your risk is higher than average. The risk is even higher if that relative was diagnosed before age 50 or if multiple relatives on the same side of the family have had ovarian, breast, or colon cancer. These patterns often point to shared genetic mutations, even if no one in the family has been formally tested.

A personal history of breast cancer also raises ovarian cancer risk. The two cancers share genetic links, particularly through BRCA mutations, and people who have had breast cancer are more likely to develop ovarian cancer than people without that history. Colon cancer in the family is relevant too, because Lynch syndrome—an inherited condition that raises colon cancer risk—also increases ovarian cancer risk.

Reproductive and hormonal factors

Several aspects of reproductive history are tied to ovarian cancer risk. Never being pregnant is associated with higher risk compared to people who have carried pregnancies to term. Each pregnancy appears to lower risk slightly, and breastfeeding may lower it further. This pattern suggests that the more times ovulation is suppressed—through pregnancy and breastfeeding—the lower the risk, possibly because ovulation itself creates cellular stress in the ovaries.

Starting menstruation early (before age 12) and reaching menopause late (after age 50) both increase lifetime ovarian cancer risk, again because they extend the total number of ovulation cycles. Long-term use of hormone therapy after menopause is associated with higher risk in some studies, though the relationship is complex and depends on the type and duration of therapy. Oral contraceptives, by contrast, appear to lower risk, possibly because they stop ovulation.

Obesity, smoking, and endometriosis

Obesity is linked to higher ovarian cancer risk in some studies, particularly for certain types of ovarian cancer. The mechanism is not fully understood but may involve inflammation, changes in hormone levels, or how the body processes estrogen. Smoking is also associated with increased risk, particularly for a subtype called mucinous ovarian cancer.

Endometriosis—a condition in which tissue similar to the uterine lining grows outside the uterus—is associated with ovarian cancer risk. People with endometriosis have roughly two to three times the risk of developing ovarian cancer compared to people without it. The connection may involve chronic inflammation, repeated cell injury and repair, or shared genetic factors, but research is still working out the details.

What does not cause ovarian cancer

Several things once suspected of raising ovarian cancer risk have not been confirmed by research. Talc powder use was long studied as a potential risk factor, but evidence remains mixed and inconclusive. Fertility treatments have been studied extensively, and most research does not show a clear link to ovarian cancer, though some studies suggest a possible small increase in risk for certain subtypes—more research is ongoing.

Ovarian cysts are common and almost always benign; having cysts does not cause cancer. Polycystic ovary syndrome (PCOS) has been studied as a potential risk factor, with some research suggesting a modest increase in risk, though this remains an area of active investigation.

Frequently Asked Questions

If I have a risk factor, will I definitely get ovarian cancer?

No. Having a risk factor means your chances are higher than average, but most people with risk factors never develop ovarian cancer. Even people with BRCA mutations, which carry the highest risk, do not all develop the disease. Risk is a probability, not a certainty.

Should I get genetic testing if no one in my family has had cancer?

Genetic testing is most useful when there is a family history of ovarian, breast, or colon cancer, or when you have had breast cancer yourself. If you have no personal or family history, testing is unlikely to find a mutation. A genetic counselor can review your family history and advise whether testing makes sense for you.

Can ovarian cancer be prevented?

There is no may provide prevention, but some steps lower risk. Oral contraceptives, pregnancy, and breastfeeding all appear to reduce risk. For people with BRCA mutations, preventive surgery to remove the ovaries and fallopian tubes significantly lowers ovarian cancer risk, though this is a major decision with its own implications.

Does my risk change as I get older?

Yes. Your absolute risk—the chance of developing ovarian cancer in the next year—increases with age, particularly after 50. However, if you reach age 70 without developing ovarian cancer, your remaining lifetime risk becomes lower simply because fewer years remain.

What should I do if I have multiple risk factors?

Talk with your doctor about your specific combination of risk factors. They may recommend more frequent screening, genetic testing, or other monitoring depending on your situation. A gynecologic oncologist or genetic counselor can help you understand what your particular risk profile means.