Hormonal contraception: benefits versus risks.Am J Obstet Gynecol. 1987 Oct; 157(4 Pt 2):1023-8.AJ
Epidemiologic studies, chiefly in English and U.S. populations, have generated concern regarding cardiovascular hazards associated with the use of oral contraceptives (OCs). A detailed analysis of these data suggests, however, that such studies have serious methodologic flaws. For example, the clinical diagnosis of deep vein thrombosis may be incorrect up to 50% of the time, rendering statistical analysis meaningless. The known cardiovascular risks of cigarette smoking may be amplified by OC use, but nonsmokers probably do not have an increased risk. Further, a number of studies in developing-world countries do not yield evidence of increased cardiovascular risks of OC use. Abnormal levels of serum lipids appear to affect cardiovascular (that is, myocardial infarction) risks in Western populations. Whether normalization of these levels improves the outlook is not entirely certain. The hormonal components of OCs are known to affect serum lipids, raising concern about possible long-term consequences. Newer low-dose OC formulations (such as triphasics) do not cause changes in serum lipids and therefore eliminate this putative risk.