Oral contraceptives and stroke.

Since 1962, more than 25 studies have been devoted to the relationship between oral contraceptives and stroke. They are all case-control or cohort epidemiological studies and thus contain the difficulties and biases that are inherent in these types of studies. The following conclusions can be drawn from these studies: High oestrogen content (> or = 50 microg) increases the risk of stroke, all stroke subtypes, and stroke death. Low oestrogen content (<50 microg) carries a very low or no risk of stroke. There are no data on progestogen only oral contraceptives. Stroke risk is greatly increased if associated risk factors are present, in particular hypertension, cigarette smoking and migraine. Oral contraceptives, even at low doses, significantly increase the risk of cerebral venous thrombosis, which is further enhanced if congenital thrombophilia is present. The attributable risk of stroke in young women using oral contraceptives is about 1 per 200000 woman-years. The contraceptive and non-contraceptive benefits of low dose oral contraceptives vastly outweigh their risks provided that other risk factors are absent or well controlled.