Oral contraceptive pills could protect women from cancer of the womb, a new medical study revealed.

According to research published in The Lancet Journal, 400,000 cases of endometrial cancer were avoided in the last half-century through oral contraceptives, known as “the pill,” half of which were prevented in the past decade.

For every five years of using oral birth control, risk of suffering the illness decreases by around a quarter.

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The study shows that risk declines in line with the length of time a women takes the pill, even years after she stops taking it.

“The strong protective effect of oral contraceptives against endometrial cancer—which persists for decades after stopping the pill—means that women who use it when they are in their 20s or even younger continue to benefit into their 50s and older, when cancer becomes more common,” said Oxford University’s Valerie Beral, who led the study.

"Previous research has shown that the pill also protects against ovarian cancer. People used to worry that the pill might cause cancer, but in the long term the pill reduces the risk of getting cancer."

The low dosages of estrogen hormones that today’s contraceptive pills carry are still sufficient to reduce the risk of uterine cancer, the study suggests, despite having halved since the 1960s.

Four out of five sexually active women in the United States have used the pill. Last year, the U.S. Supreme Court ruled that owners of private companies can object on religious grounds to a provision of President Barack Obama's healthcare law that requires employers to provide insurance covering birth control for women.

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