British researchers found that:
Birth control pills can protect women against ovarian cancer for 30 years or longer after they stop taking them and have so far prevented 100,000 ovarian cancer deaths worldwide.
The longer women stay on the pill, the lower their risk of developing the disease, which is more common after age 50... For example, women who take the pill for 15 years cut their risk in half.
Also,
When you are 60 it matters whether you took it for five years or 10 years in your twenties, the longer you took it, the better off you are when the risk of ovarian cancer is high.
The study found that:
Taking the pill for 10 years cut the risk of ovarian cancer before the age of 75 from 12 per 1,000 women to 8 per 1,000. It also reduced the risk of dying from the disease from 7 per 1,000 women to 5 per 1,000 before the age of 75.
The study also showed ethnicity, education, family history and other factors do not seem to make much difference in reducing risk when it comes to using the pill.
