> nearly all the research on the link between oral contraceptives and cancer risk comes from observational studies, both large prospective cohort studies and population-based casecontrol studies. data from observational studies cannot definitively establish that an exposurein this case, oral contraceptivescauses (or prevents) cancer. that is because women who take oral contraceptives may differ from those who dont take them in ways other than their oral contraceptive use, and it is possible that these other differencesrather than oral contraceptive useare what explains their different cancer risk aka you cant prove it!
United States