A new research presented the 2015 National Cancer Research Institute Cancer Conference in the UK explained that having a lot of children or having the fallopian tubes cut change the risk of various types of ovarian cancer.  Ovarian cancer mortality rate is higher than any other cancer of the female reproductive system. Evidence now leads to different types of ovarian cancer with distinct origins; however they are still grouped together because they are first found in the ovaries.

The chances of a woman having each type may be caused by her reproductive history. Experts have found for some time that the number of children a woman has and her use of contraception can greatly influence her risk of ovarian cancer. A team headed by Dr. Kezia Gaitskell, a pathologist based at the Cancer Epidemiology Unit of the University of Oxford, went out of their way to find out more about different types of the disease. They used the data from the UK Million Women Study, which is a longitudinal study of 1,146,985 women aged over 50 at recruitment. There were 7,570 incident cases of ovarian cancer recorded after an average of 13 years of follow-up.

Having one child decreases the risk by 20%. The risk of the four most common types of ovarian cancer was analyzed in women with different childbearing patterns: serous, mucinous, endometrioid and clear cell tumors. Women with one child had a 20% decrease in overall risk of ovarian cancer, compared to women without children.  They also have approximately 40% reduction of risk for endometrioid and clear cell tumors. Each additional birth lowers the overall risk of ovarian cancer by about 8%.

Whether or not they tried breastfeeding seems to have no difference, although longer durations of breastfeeding appear to diminish the risk. The researchers also checked the risk for women who had been under the knife to cut or clip their fallopian tubes, a surgical procedure for permanent contraception commonly called tubal ligation, or sterilization. The procedure seems to lessen the overall risk of ovarian cancer by 20%. It also cut down the risk of high-grade serous tumors, the most common type of ovarian cancer, by 20% and the risk of endometrioid and clear cell tumors by 50%.

Dr. Gaitskell believes that tubal ligation may reduce the risk by acting as a wall that prevents the abnormal cells from passing through the fallopian tubes to the ovaries. She explains that the moment it was discovered that ovarian cancer doesn't always originate in the  ovaries, people's perception of the disease has greatly changed.