Cardiovascular disease and steroid hormone contraception. Report of a WHO Scientific Group.

Over 90 million women worldwide, including over 44 million in developing countries, are now using oral contraceptives. Despite their advantages, there is concern about the links between combined oral contraceptives and the risk of cardiovascular disease. Although most contraceptive users are healthy with a low background incidence of major disease, the very large number of women using oral contraceptives throughout the world means that even modest elevations in risk have the potential to affect a large number of women. This report presents the conclusions of a WHO Scientific Group that met to discuss the association between use of steroid hormone contraceptives (including combined oral contraceptives) and the risk of cardiovascular disease in women. The Scientific Group evaluated the data available from case-control and cohort studies on acute myocardial infarction, ischaemic and haemorrhagic stroke, and venous thromboembolism. The Group also reviewed the data on possible biological mechanisms for the effects of combined oral contraceptives on cardiovascular disease, including the interplay between lipoprotein metabolism, humoral regulators such as insulin, coagulation and fibrinolysis, the products of the endothelium of blood vessels and the renin-angiotensin-aldosterone system. The Group identified factors which may predict, for individual women, an increased risk of cardiovascular effects with use of different hormonal contraceptives, and assessed whether the various compositions of combined oral contraceptives have different risk profiles for cardiovascular disease. The report presents the Group's conclusions relating to the various types of cardiovascular disease in women of reproductive age, together with a list of recommendations for further research.