Oral contraception and myocardial infarction revisited: the effects of new preparations and prescribing patterns.

All deaths from myocardial infarction occurring during 1978 in women aged 15-44 years in England and Wales have been investigated. Using a case-control approach, oral contraceptives were found to be associated with an approximately two-fold increase in risk of this condition, but the effect was apparent only in women with no known risk factors for ischaemic heart disease. Preparations containing 30 micrograms or less oestrogen were associated with the same risk as those containing 50 micrograms oestrogen, but this could be due to the fact that preparations containing less oestrogen tend to contain higher doses of progestogens. Oral contraceptives appear no longer to be prescribed for women with recognised coronary risk factors and this improved prescribing practice has probably resulted in a substantial decrease in mortality attributable to oral contraceptive use.