Ovarian cancer occurs when genetic mutations (variations) in cells cause tumors to form on or in the ovaries. Tumors of the fallopian tubes and the peritoneum (the lining of the inside of the abdomen) are often grouped together with ovarian cancer because they have similar causes, symptoms, and treatment plans.

Ovarian cancer is caused by genetic mutations that allow cells to divide and grow in a disorganized way. There are two main types of mutations, inherited and acquired.

Inherited mutations:

• Are passed down from parents to children
• Are present in the DNA of all cells at birth
• Occur far less commonly than acquired mutations

Acquired mutations:

• Happen over the course of a person’s life
• Are caused by normal aging and exposure to carcinogens, such as radiation, certain chemicals, and smoking
• Are present in the DNA of some cells

Inherited mutations that run in families play a role in up to 25 percent of ovarian cancer cases, but most cancer is caused by acquired mutations. The cause of ovarian cancer is usually unknown.

How Cells Transform Into Cancer

Normal cells divide in a regular, ordered fashion, forming new cells that are exact copies to replace old ones. Certain genes in each cell are responsible for telling cells when to divide and when to stop dividing. Other genes identify and fix problems in DNA that are copied incorrectly, or cause cells with bad DNA to self-destruct rather than keep multiplying.

If a genetic mutation causes one or more of these genes to turn off in some cells, the cells can divide at a faster rate without regulation or order, becoming more and more mutated.

Mutations may accumulate, further speeding the unchecked growth of abnormal cells. When these disordered cells begin to invade nearby tissues or break off and migrate to other locations, they have become cancerous.

Risk Factors for Ovarian Cancer

It is important to note that while science is good at finding correlations — or apparent relationships — between factors and disease, correlation does not prove the factor causes the disease. Many risk factors for ovarian cancer have been identified and are being studied for their role in the development of the disease.

Since genetic mutations cause ovarian cancer, risk factors for ovarian cancer include anything that can encourage mutations. Any woman in the general population of the U.S. has about a 1.1 percent chance of developing ovarian cancer in her lifetime, according to the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) Program. Inherited mutations from one’s parents and acquired mutations from age or environmental or lifestyle factors may raise or lower that risk.

Inherited Factors

Up to 25 percent of ovarian cancers are thought to be influenced by genes inherited from parents. If you have a family history of ovarian cancer, your own risk is increased. When a particular gene mutation that is strongly linked to cancer is passed down within a family, it is called a family cancer syndrome.

Hereditary breast and ovarian cancer (HBOC) is a family cancer syndrome that can lead to ovarian or breast cancer, as well as other cancers such as pancreatic cancer. Individuals with HBOC tend to develop cancer at a younger age or get cancer multiple times. When ovarian cancer runs in families, 65 percent to 85 percent of the time it is caused by mutations in the BRCA1 and BRCA2 genes.

The BRCA genes are needed by cells to repair damage. They are known as “tumor suppressor” genes, and they help prevent cells from turning cancerous. In people with an inherited mutation in one of the BRCA genes, damage can pile up in the cell, leading to additional acquired mutations that cause cancer. BRCA1 and BRCA2 gene mutations raise the risk for developing cancer, but not every person with these mutations will get cancer. Women with a BRCA1 mutation have a 40 percent to 60 percent chance of developing ovarian cancer, according to MedlinePlus. Those with a BRCA2 mutation have a 20 percent to 35 percent chance.

Other family cancer syndromes associated with ovarian cancer are caused by different gene mutations. For example, Lynch syndrome is caused by mutations in the repair genes MLH1, MSH2, and MSH6. Lynch syndrome increases a person’s chance of colon, ovarian, stomach, pancreas, kidney, and brain cancers.

Cancer may also run in a family, but no known gene mutation can be found. If ovarian cancer runs in your family, genetic testing may help you learn whether you are at increased risk.

Environmental Factors

Researchers have identified a wide array of environmental factors linked to the development of ovarian cancer. We are all exposed to risk factors throughout our lives. Some are avoidable, while others are outside our control. Anything that raises the risk for acquired gene mutations also raises the risk for developing ovarian cancer.

Age

Mutations in DNA are inevitable. The older you get, the more acquired mutations you will accumulate. However, cancer only develops in a small percentage of people.

A person’s risk for developing ovarian cancer increases with age. While a few types of ovarian cancer are found in younger women, most cases of ovarian cancer occur in middle-aged or older women. Half of ovarian cancer diagnoses happen in women who are at least 63 years old, according to the American Cancer Society.

Exposure to Hormones

There is a link between ovulation, or the release of an egg from an ovary, and ovarian cancer risk. Experts think this may be because the more someone is exposed to estrogen, a reproductive hormone that predominates in females, the more likely they are to get cancer. Going through more cycles of ovulation raises risk, and things that block ovulation cause risk to decrease.

Factors that increase a person’s number of ovulations or estrogen levels, and increase ovarian cancer risk, include:

• Starting menstruation early, before age 12
• Entering menopause late, after age 55
• Never having been pregnant
• Using hormone replacement therapy after going through menopause
• Never having used hormonal birth control, such as oral contraceptives

On the other hand, those who have had fewer ovulations have a lower chance of developing ovarian cancer. Hormone-related factors that decrease a person’s risk of ovarian cancer are:

• Pregnancy — Each pregnancy decreases ovarian cancer risk.
• Breastfeeding
• Using hormonal birth control — The longer a person takes birth control pills, the lower their risk.

Some surgeries can also have an effect. Getting tubal ligation, or having the “tubes tied,” can lower a person’s risk for ovarian cancer by 67 percent, according to the Ovarian Cancer Research Alliance (OCRA). Having a hysterectomy (surgery to remove all or part of the uterus) can lower risk by 33 percent.

Radiation

High doses of radiation may increase a person’s chance of getting ovarian cancer. For example, nuclear workers or people exposed to atomic bombs are more likely to get ovarian cancer. However, this does not appear to be true for low doses of radiation. In one study in the Asian Pacific Journal of Cancer Prevention, women who had previously gotten radiation treatments for other types of cancer were less likely to get ovarian cancer.

Chemicals

Some types of chemicals can increase the risk of various cancers. This hasn’t been well studied in ovarian cancer, but some data shows that chemicals such as pesticides, herbicides, or talcum powder may lead to higher risk. However, other studies have not shown a strong link between talcum powder and ovarian cancer risk. More research is needed to fully understand whether an association exists and to what degree.

Smoking

Smoking cigarettes increases a person’s risk of mucinous ovarian cancer, but it may not be linked to other types of ovarian cancer. People who smoke tend to have worse outcomes for ovarian cancer.

Diet

Some research has shown that eating high amounts of animal fats increases a person’s risk of ovarian cancer. Animal fats are found in red meat and dairy products, such as milk, butter, and cheese.

Obesity

Being overweight is linked to several types of cancer. Experts don’t yet know for sure how ovarian cancer risk is affected, but some data shows that people with obesity — those with a body mass index (BMI) of 30 or higher — may be more likely to develop some types of lower-grade ovarian tumors — tumors in which cancer cells appear more like normal cells under a microscope.

In Vitro Fertilization

Some people use in vitro fertilization (IVF) to help them get pregnant. While some research has found that IVF increases the risk of lower-grade ovarian tumors, other studies have not found a strong link. If you are considering going through IVF or have used it in the past, your doctor can help you understand whether fertility drugs could increase your risk of ovarian cancer.

History of Cancer or Endometriosis

Sometimes, having had another health condition or another type of cancer makes your risk of ovarian cancer higher. People who have had breast, uterine, rectal, or colon cancer may have an increased chance of getting ovarian cancer. Additionally, having endometriosis raises your risk of getting endometrial or clear cell ovarian cancer.

Race and Ethnicity

Ovarian cancer incidence varies significantly by race and ethnicity. According to a 2017 meta-analysis of 19 past studies, non-Hispanic white women have the highest incidence of epithelial ovarian cancer (the most common form of ovarian cancer) in the U.S., followed by Hispanic, Asian/Pacific Islander, and Black women. Multiple factors contribute to these differences, including variations in reproductive, hormonal, and lifestyle risk factors.

Hispanic women have a slightly higher incidence of ovarian cancer compared to Black women but lower than non-Hispanic white women, according to the analysis. However, among those with a family history of breast or ovarian cancer, their risk is increased. The association between certain risk factors, such as parity (number of times a person gives birth) and oral contraceptive use, tends to be consistent across racial and ethnic groups, although some variations are observed.

Asian/Pacific Islander women have a lower overall incidence of ovarian cancer compared to non-Hispanic white women and Hispanic women, according to the analysis. The protective effect of parity is particularly strong in this group, with the risk of ovarian cancer decreasing as the number of births increases.

Black women have the lowest overall incidence of ovarian cancer among the groups represented in the analysis. One study found that Black women with a family history of breast or ovarian cancer have a higher risk of developing the disease compared to other racial groups. Additionally, Black women are more likely to have a hysterectomy, a procedure associated with an increased risk of ovarian cancer in this population.

Can Ovarian Cancer Be Prevented?

Unfortunately, there is no guaranteed way to make sure you don’t get cancer. Some people have a lot of risk factors and don’t get the disease, while the majority of individuals who are diagnosed don’t have any risk factors. Additionally, most risk factors like age and genetic predisposition are beyond anyone’s control. If you are concerned that you may have a higher risk for developing ovarian cancer, focus on lowering your risk by changing the environmental factors within your control.

If you think you may be at an increased risk, keep an eye out for some of the symptoms of ovarian cancer, such as bloating, abdominal pain, or frequent urination. Talk to your doctor to learn more about how your own individual characteristics may affect your chance of developing cancer.