Oral contraceptives and myocardial infarction. The risk of myocardial infarction in contraceptive users is limited to women over 35 years of age who smoke. The cause of myocardial infarction in oral contraceptive users is thrombotic and not atherosclerotic. Minor lipid changes have no clinical relevance to myocardial infarction in contraceptive pill users and do not appear to increase coronary plaques. 