Past studies have shown that the pill affords some protection against ovarian cancer, but researchers did not know how long this beneficial effect lasted.
In a new study led by Valerie Beral from the Cancer Research UK Epidemiology Unit at Oxford University, researchers compiled data from 45 previous studies that included about 23,000 women with ovarian cancer and 87,000 without it.
Just over 30% of the women with cancer and 37% of those without cancer had taken the pill for some period of time.
The authors of the study, published in The Lancet, found that using the pill for a decade or more reduced ovarian cancer risk by almost one-third and the protection lasted 30 years after pill usage had stopped.
They also found that the longer a woman was on the pill the more it reduced cancer risk.
This beneficial effect was consistent, regardless of ethnicity, education, or alcohol and tobacco consumption, they found.
"Women do not have to worry about bad side effects from taking the pill," said Beral. "We know now that the pill actually offers protection against ovarian cancer."
The authors of the study estimate that 30,000 deaths from ovarian cancer could be prevented every year by the use of birth control, however, this is the first study to look at long-term benefits of the pill and more work is needed to confirm the results.
