Updated August 26, 2014.

It is not completely clear what causes ovarian cancer. Because of this, it is difficult to focus efforts on specific mechanisms for prevention. No effective screening tests are available. So, what can you do to reduce your risk of developing ovarian cancer?
 

Dietary Factors

First, consider your diet. Some studies suggest an association with a Western diet high in fat, refined sugar and red meat. Other reports suggest an increased risk with obesity.

Although published studies are not all in agreement, flavonoids, which are antioxidant compounds found in plants, fruits, vegetables and tea, may be protective. Finally, Omega-3 fish oils have also been shown to lower risk. On balance, the data suggest that what you eat may affect your risk. However, while avoiding a fast-food high fat and high refined sugar Western diet may be prudent, the details of an ideal diet remain unclear.
 

Pregnancy and "The Pill"

Pregnancy and oral contraception have been proven to reduce risk in multiple epidemiologic studies. Basically, the more years your ovaries are in a dormant non-ovulatory state, due to pregnancies or because of oral contraception, the lower the risk. The exact mechanism of prevention is unknown. It is felt to be related to either less trauma to the ovaries or a direct hormonal effect from progesterone (a hormone).
 

Vitamin A

Fenretidine, a synthetic type of Vitamin A, may protect women against both breast and ovarian cancer. Although the scientific studies are not all in agreement, the evidence is from multiple types of experimental studies including animal data, epidemiologic data and clinical trials.

A large international randomized clinical trial is currently under way.
 

Pain Relievers

Acetominophen and ibuprofen, common pain relief products, have both been shown to reduce the risk of ovarian cancer; not so with aspirin use. The way they do this is not clear, but may be due to reducing ovulation or a biochemical effect on something called the COX-2 cyclooxygenase pathway.
 

Surgical Options

Although not recommended as an intervention to reduce ovarian cancer risk, there are at least seven studies that all show tubal ligation protects against ovarian cancer. If you have had a tubal ligation you are at lower risk, but no physician will agree to a tubal ligation for the sake of prevention alone. The same goes for hysterectomy without removal of the ovaries. There is a preventive effect, but the mechanism remains unclear.

Removal of the ovaries is the most direct surgical way to reduce risk and is commonly recommended to patients who are at high risk due to family history or have tested positive for BRCA1 or BRCA2 gene alteration. A large clinical trial has recently concluded and we are all waiting for the data to mature. What this means is that we have to wait a while to see if removal of the ovaries in the women who were enrolled in this large study will indeed prevent ovarian cancer over the next few years.

Results from multiple studies prior to this one strongly suggest that this strategy works to prevent 99% of ovarian cancers in those who have undergone ovarian removal. A very similar cancer that affects the entire internal abdominal lining, called primary peritoneal cancer, can still occur despite removal of the ovaries. The main question that remains is which women are at high enough of an ovarian cancer risk to justify the risks of surgery.
 
_Source:

Ovarian Cancer Prevention Statement:American Cancer Society.