Birth Control Pills May Reduce Endometrial Cancer Risk

oral contraceptives
According to a new study, birth control pills may reduce a woman's risk for endometrial cancer by 25 percent for every five years of use. Eric Gaillard/Reuters

Birth control pills can have a number of positive health benefits that go beyond avoiding unwanted pregnancy, including lighter and less painful periods, reduced symptoms of premenstrual syndrome and even fewer pimples. Now new research suggests we can add cancer prevention to the list.

A paper published Wednesday in The Lancet Oncology estimates that in the last 50 years, oral contraceptives have prevented approximately 400,000 deaths from endometrial cancer.

The paper looked at 36 existing studies over five decades that involved data on 27,276 women diagnosed with endometrial cancer in North America, Europe, Asia, Australia and South Africa.

The researchers found that for every five years a woman used birth control pills, she reduced her risk for endometrial cancer by about 25 percent. In higher-income countries, the risk reduction was even more pronounced: There were only 1.3 cases of endometrial cancer per 100 women who used oral contraceptives compared with 2.3 per 100 women who didn't take the pill.

"This really helps to quantify it in a way doctors and patients can understand," says Dr. Jennifer Wu, an obstetrician and gynecologist at Lenox Hill Hospital in New York City. "It's really important for a patient to realize that there are these benefits."

Though hormone levels in oral contraceptives have decreased considerably over the last few decades, the study indicates that women who took the pill in the 1960s appeared to have as much protection from endometrial cancer as those who took the pill in the 1980s. After adjusting for factors such as a woman's body mass index, alcohol and tobacco use, reproductive history and ethnicity, the researchers found women who had a history of oral contraceptive use also were less likely to develop endometrial cancer.

The authors of the study note that prior research has shown birth control pills may reduce a woman's risk for ovarian cancer, another type of reproductive cancer that strikes women late in life. One analysis of 55 previously published studies found the pill could reduce a woman's risk for ovarian cancer by more than 50 percent.

Wu explains the female hormones in birth control pills prevent a thickening of the uterine wall, which can lead to the development of abnormal, precancerous cells that proliferate and then eventually become malignant. Women on birth control pills will have a thinner uterine lining and therefore a smaller risk for this type of cancer. However, there are some health conditions related to long-term use of birth control pills. Though the occurrence is rare, oral contraceptives are linked to higher risk for liver cancer, high blood pressure, stroke and blood clots. One recent study suggests use of certain types of birth control pills—specifically ones with higher doses of estrogen—may raise a woman's risk for breast cancer.

Approximately 54,870 women will be diagnosed and 10,170 will die from endometrial cancer this year in the U.S., according to the American Cancer Society. The average age for diagnosis is 60, and the disease is especially rare in women under 45. This suggests that the oral contraceptives taken during childbearing years may provide protection from this type of cancer in the postmenopausal years.