Research has found that women who take combined oral contraceptives have a slightly increased risk of breast cancer compared with women who have never used them. This risk seems to return to normal once the pills are stopped, however. Women who took birth control pills more than 10 years ago do not appear to have any increased risk of breast cancer.Later in life, the use of combined hormone therapy after menopause—progesterone and estrogen—increases breast cancer risk. According to the Women's Health Initiative (WHI), women who took a combination of progesterone and estrogen were more likely to develop breast cancer, and breast cancers in these women were larger and more likely to have spread to the lymph nodes once they were diagnosed. The number of breast cancers in these women increased with the number of years they took combined hormone therapy and decreased once they stopped taking it. The WHI also revealed combined hormone therapy made mammograms less effective and less likely to detect breast cancer in the early stages.However, when you look at the actual numbers, the relative increased risk is fairly low. The rate of breast cancer in people taking estrogen plus progestin in the WHI was 2.6 per 10,000 women, and the rate was 1.3 per 10,000 in women taking a placebo.