Ovarian cancer has no single cause, but rather a combination of genetic, hormonal, and lifestyle factors that raise or lower risk over a woman’s lifetime. The median age at diagnosis is 63, and roughly half of all cases occur in women between 55 and 74. Understanding what drives risk can help you make sense of your own situation or family history.
Genetics and Family History
Inherited gene mutations are the strongest known risk factor. Women who carry a harmful change in the BRCA1 gene have a 39% to 58% lifetime chance of developing ovarian cancer. For BRCA2 carriers, that range is 13% to 29%. Compare that to the general population risk of about 1.1%. These mutations also increase breast cancer risk, which is why they often come up together in genetic counseling.
Lynch syndrome, a hereditary condition caused by faulty DNA repair genes, also raises ovarian cancer risk. The two genes most strongly linked are MSH2 and MLH1, which carry lifetime ovarian cancer risks of 8% to 38% and 4% to 20%, respectively. Other Lynch-associated genes (MSH6 and PMS2) don’t appear to increase ovarian cancer risk nearly as much, if at all. Lynch syndrome is more commonly associated with colorectal and uterine cancers, so ovarian risk can be overlooked in affected families.
Even without a known mutation, having a first-degree relative (mother, sister, daughter) with ovarian cancer increases your risk. If genetic testing is something you’re considering, it’s worth knowing that mutations account for roughly 20% to 25% of ovarian cancers overall, meaning most cases occur in women with no identifiable inherited cause.
How Ovulation Itself Creates Risk
One of the most well-supported theories in ovarian cancer research centers on ovulation. Each time an egg is released, the surface of the ovary ruptures and must repair itself. That rupture triggers an inflammatory response: the body sends immune cells to the area, and those cells generate reactive oxygen species, molecules that can damage DNA. Normally, the body’s built-in tumor suppression systems catch and repair that damage. But over decades of monthly ovulation, the sheer number of repair cycles increases the chance that a mutation slips through uncorrected.
This “incessant ovulation” theory helps explain why factors that reduce the total number of ovulations, like pregnancy, breastfeeding, and oral contraceptive use, are consistently linked to lower risk. It also helps explain why ovarian cancer is more common in women who started menstruating early or reached menopause late, since both extend the total years of ovulation.
Hormonal Factors
Postmenopausal hormone therapy increases ovarian cancer risk regardless of whether a woman takes estrogen alone or a combination of estrogen and progestagen. A large meta-analysis pooling data from 52 studies found that current or recent users had a 37% higher risk compared to women who never used hormone therapy, and even short-term use (under five years) carried a meaningful increase. The risk gradually declines after stopping, but roughly 10 years after discontinuing long-term therapy, there’s still a detectable excess of the two most common tumor types: serous and endometrioid.
To put that in practical terms: for every 1,000 women who use hormone therapy for five years starting around age 50, about one additional ovarian cancer case is expected. That’s a small absolute increase, but it’s worth weighing against the benefits of hormone therapy for managing menopause symptoms.
Reproductive History and Breastfeeding
Pregnancy and breastfeeding both lower risk, and the mechanism ties back to ovulation suppression and hormonal shifts. A meta-analysis covering more than 17,000 women with ovarian cancer found that any history of breastfeeding was associated with a 30% reduced risk compared to never breastfeeding. The protection followed a clear dose-response pattern: less than six months of total breastfeeding reduced risk by about 15%, six to twelve months by about 27%, and more than twelve months by about 36%. Each additional stretch of breastfeeding added measurable protection.
Women who have never been pregnant face higher risk than those who have, and having multiple pregnancies further reduces risk. Again, fewer total ovulations appears to be the common thread.
Oral Contraceptives and Risk Reduction
Birth control pills are one of the most consistent protective factors identified in ovarian cancer research. Women who have ever used oral contraceptives have a 30% to 50% lower risk than women who never have. The protection grows with longer use and persists for up to 30 years after stopping. This is one reason some doctors discuss oral contraceptives as a risk-reduction strategy for women with BRCA mutations or strong family histories, though the decision involves weighing other health considerations.
Endometriosis
Endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus, is linked to specific subtypes of ovarian cancer. Women with endometriosis have a 3.4 times higher risk of clear cell ovarian cancer and a 2.3 times higher risk of the endometrioid subtype. These are less common subtypes than serous ovarian cancer (which makes up the majority of cases), but they’re important to be aware of if you have a history of endometriosis. The chronic inflammation and hormonal environment created by endometriosis are thought to drive this connection.
Body Weight
Carrying excess weight increases ovarian cancer risk in a dose-dependent way. For every five-point increase in BMI, the risk of ovarian cancer rises by about 6%. A woman with a BMI of 35 faces roughly 12% more risk than a woman with a BMI of 25. The connection likely involves the hormonal changes that accompany excess body fat, particularly higher circulating levels of estrogen and insulin, both of which can promote cell growth. This is one of the few modifiable risk factors for ovarian cancer.
Talcum Powder
The link between genital talc use and ovarian cancer has been studied and debated for decades. A study from the National Institute of Environmental Health Sciences analyzing data from over 50,000 women found a persistent positive association between genital talc use and ovarian cancer. The strongest associations appeared in women who used talc frequently, over long periods, and during their reproductive years. No similar link was found for breast or uterine cancer. The biological theory is that talc particles can travel through the reproductive tract and cause chronic inflammation at the ovaries, but the evidence remains less definitive than for genetic or hormonal factors.
Age and Who Is Most Affected
Ovarian cancer is predominantly a disease of older women, though it can occur at any age. Nearly half of all new cases (48%) are diagnosed in women between 55 and 74. About 16% of cases occur in women 45 to 54, and another 16% in women 75 to 84. Only about 6% of cases are diagnosed in women under 35. The risk accumulates over time as cells divide and the chances of uncorrected DNA damage grow, which is why age alone is one of the most significant risk factors.
There is no reliable screening test for ovarian cancer in the general population. Neither CA-125 blood tests nor transvaginal ultrasound have been shown to reduce deaths when used for routine screening. This makes awareness of risk factors especially important, since early symptoms like bloating, pelvic pain, and changes in urinary habits are easy to dismiss as something else entirely.