Combined oral contraceptives and the risk of myocardial infarction.

The studies on the combined oral contraceptive (COC) pill and myocardial infarction are reviewed. A reasonable conclusion is that the COC pill causes a two-fold increase in the risk of myocardial infarction. There is a marked interaction with smoking. The pill causes coagulation changes and affects lipoprotein and carbohydrate metabolism and these changes provide a plausible explanation for its effect. However, there are dangers in using these surrogate end-points to predict which pills carry the greatest risk. This must depend on an assessment of the epidemiology, and at present third generation pills have not convincingly been shown to be safer in this regard. The risk of causing myocardial infarction in non-smokers is small but we should be wary of prescribing the pill to smokers over 34 years old and especially to smokers over 39 years old.