A new study of more than 300,000 women, 878 of whom developed ovarian cancer over an almost 10 year period, showed that women who took oral contraceptives (The Pill) had almost half the rate of ovarian cancer as those who did not. The study showed that women taking the Pill for 10 years had a 45% reduction in risk of developing ovarian cancer. Having children was associated with a reduced risk of ovarian cancer of 29%, and each additional child was associated with another 8% reduction in risk. Advanced age at menopause was also associated with higher risk.
The abstract of the article can be found here
A press release can be found here