Haemorrhagic Stroke

Haemorrhagic strokes in users of steroid contraceptives have been examined in various ways. Some studies have considered only episodes of subarachnoid haemorrhage, whereas others have included other types of cerebral haemorrhage. In 1973, the Collaborative Group for the Study of Stroke in Young Women (1) reported that the risk of haemorrhagic stroke in current users of oral contraceptives was twice that among non-users. Although not statistically significant, this result provided the first suggestion that users of oral contraceptives may be at increased risk of haemorrhagic as well as ischaemic stroke.

Most recent studies have found smoking and hypertension to be important independent risk factors for haemorrhagic stroke. Only the WHO study (2), however, had sufficient statistical power to examine the risk of haemorrhagic stroke in women with different characteristics. In both developing and European countries, current users of combined oral contraceptives aged 35 years or more had a significantly increased relative risk of haemorrhagic stroke compared with non-users, but younger users did not. The relative risk of haemorrhagic stroke in current users of combined oral contraceptives who smoked was 3–4 times that of non-users who did not smoke. Compared with non-users without a history of hypertension, current users with such a history had a substantially higher relative risk of haemorrhagic stroke. The relative risk was not affected by whether the woman reported having had her blood pressure checked before the current episode of use.

The Scientific Group found no evidence to date that either the estrogen or the progestogen constituents of combined oral contraceptives affect the risk of haemorrhagic stroke. Sufficient data were also not available on the risk of haemorrhagic stroke associated with use of the various types of progestogen-only contraceptives.

The Scientific Group concluded that:

• The incidence of fatal and non-fatal haemorrhagic stroke is very low in women of reproductive age in both developed and developing countries.

• In women aged less than 35 years, who do not smoke, and who do not have hypertension, the relative risk of haemorrhagic stroke associated with use of combined oral contraceptives is not increased. There is no increase in the risk of haemorrhagic stroke with increasing duration of use of oral contraceptives. Women who have previously used oral contraceptives are at no greater risk of haemorrhagic stroke than women who have never used them. These conclusions appear to apply equally in developed and developing countries.

• Women with hypertension have an increased absolute risk of haemorrhagic stroke. The relative risk of haemorrhagic stroke in current users of combined oral contraceptives with hypertension may be 10 times that in current users without hypertension. This conclusion appears to apply equally in developed and developing countries.

• The risk of haemorrhagic stroke in women who smoke is up to twice that in non-smokers; in women who are current users of combined oral contraceptives and who smoke, the relative risk is about 3. This conclusion appears to apply equally in developed and developing countries.

• The incidence of haemorrhagic stroke increases with age, and current use of combined oral contraceptives appears to magnify this effect of aging.

• There is no evidence that either the estrogen or the progestogen constituent of combined oral contraceptives is related to the risk of haemorrhagic stroke. 

References

1. Collaborative Group for the Study of Stroke in Young Women. Oral contraceptives and increased risk of cerebral ischaemia or thrombosis. New England journal of medicine, 1973, 288:871–878.

2. WHO Collaborative Study of Cardiovascular Disease and Steroid Hormone Contraception. Haemorrhagic stroke, overall stroke risk, and combined oral contraceptives: results of an international multicentre case–control study. Lancet, 1996, 348:505–510.

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