Forty years after oral contraceptives were introduced in the United States, results of the Women's Contraceptive and Reproductive Experiences (Women's CARE) study of more than 10,000 women nationwide seem to put an end to the long-held hypothesis that use of oral contraceptives increases risk for breast cancer. The study included both white and African American women ages 35 to 64 years, but it did not address the risks and benefits of using oral contraceptives after menopause as hormone replacement therapy.

"Women using oral contraceptives should be reassured from this study, as it confirms that birth control pills do not increase a woman's risk of getting breast cancer," says Kathy Helzlsouer, M.D., M.H.S, of Johns Hopkins University, in the accompanying editorial. The investigators also report that several similar studies show oral contraceptives reduce the risks of uterine and ovarian cancers by as much as 40 percent.

The Women's CARE study comes after an analysis of worldwide studies on oral contraceptive use found a slight increase in breast cancer risk among women who used the medication. In the editorial reviewing the current study, authors assert that the researchers accounted for long-term oral contraceptive use and a wide range of estrogen and progesterone doses.

Although the experts conclude that, for most women, the benefits of taking oral contraceptives outweigh the risks, they caution use is not without risk. Although the complications are rare, oral contraceptives are associated with an increased risk of other conditions including blood clots, stroke, and liver cancer, as well as myocardial infarction in women over 35 years who smoke and cervical cancer in women infected with human papillomavirus.