Combined oral contraceptives: risks and benefits.

By the age of 25 years, more than 95% of sexually active women have been exposed to combined oral contraceptives (COCs). Any effects associated with their use, therefore, carry important public health implications. COCs exert major protective effects against ovarian and endometrial cancer, which continue many years after cessation of use. COCs increase the risk of cardiovascular disease, but this risk is probably confined to current users. It is unclear whether lower dose preparations carry less risk. The precise relationship between COC use and risk of breast and cervical cancer is uncertain, although it is clear that COCs do not influence the overall risk of breast cancer. The risk-benefit equation for COC use depends crucially on assumptions about the true breast cancer risk. If there is no increased risk then COCs have a net beneficial effect on mortality, mainly due to the saving in ovarian cancer deaths. However, with more pessimistic assumptions about breast cancer, COCs have an adverse effect. The risk-benefit equation will vary for individual women. Most research has related to the developed world and extrapolation of findings to developing countries is inappropriate.