Oral contraceptives have prevented 200,000 cases of endometrial cancer in the last decade, according to new research published Tuesday.

In the new study, published in the journal The Lancet Oncology, researchers looked at data from 27,276 women with endometrial (uterine) cancer and 115,743 women without it from 36 different studies. They estimate in their findings that 400,000 cases of endometrial cancer have been prevented due to women taking oral contraceptives in the past 50 years, and 200,000 of these prevented cases are from the last 10 years.

The study shows that every five years of using oral contraceptives lowers the risk of endometrial cancer by around a quarter. Hormone doses in oral contraceptives have dropped through the years, but the new findings suggest that the amount of hormones in lower dose pills used today still offer a protective benefit.

Since oral contraceptives make the body think its pregnant, the amount of natural estrogen circulating in the body drops and lowers the risk of developing endometrial cancer.

The study also found that the longer the women used oral contraceptives, the greater their risk declined. Interestingly, the risk reduction continued for over 30 years after the women stopped using oral contraceptives, suggesting the protective effect is prolonged.

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