Although no one knows exactly why oral contraceptives and pregnancy protect the ovaries, they know both reduce the number of times that a woman's reproductive hormones stimulate monthly ovulation and menstruation. Less exposure to that hormonal flux might lower the risk of ovarian cancer. Women who reach menopause later in their lives may have a greater ovarian cancer risk because of prolonged exposure to hormonal fluctuations.
The study found that breastfeeding, the age at which a woman begins menstruating and the age at which she first becomes pregnant had no effect on ovarian cancer risk.
Hiom of Cancer Research UK noted that the risk of ovarian cancer increases as women grow older. "Most cases are in women who are past their menopause," she said.
Ovarian cancer spreads quickly and is particularly deadly in older women, according to two presentations Wednesday at the American Association for Cancer Research Frontiers in Cancer Prevention Research conference in Boston. In both studies, women's use of oral contraceptives reduced the risk of fatal ovarian cancer, MedPage Today reported.