Since oral contraceptives have been used by more than 40 million
American women, an association between oral contraceptives and
ovarian cancer could have a substantial public health impact.
The Centers for Disease Control, Atlanta, is studying this
relationship as part of a multicenter, case-control study—the
Cancer and Steroid Hormone Study. During the first ten months of
the study, we enrolled 179 women aged 20 to 54 years who had
been ascertained to have newly diagnosed ovarian cancer by eight
population-based cancer registries. From the general population
of those eight areas, we selected as controls 1,642 women with
intact ovaries. Users of oral contraceptives had an age-adjusted
risk of ovarian cancer developing of 0.6 relative to those who
had never used them (95% confidence interval, 0.4 to 0.9). The
risk of ovarian cancer decreased with increasing duration of
oral contraceptive use and remained low long after cessation of
use. These results were not accounted for by parity,
infertility, or other pote