Recent research highlights a significant health concern regarding the use of combined hormonal contraceptives by women. These contraceptives, commonly used worldwide to prevent pregnancy and regulate menstrual cycles, have been linked to an increased risk of cryptogenic stroke — a sudden and serious type of stroke without an apparent cause.
Cryptogenic strokes constitute nearly 40% of all strokes in younger adults, particularly women. This raises the possibility that sex-specific factors, such as hormonal contraceptive use, may contribute to this risk.
Findings from an international study involving 608 patients aged 18 to 49 with cryptogenic ischemic stroke across 13 European countries revealed that women using combined oral contraceptives (containing both synthetic oestrogen and progestogen) were significantly more likely to experience a cryptogenic stroke compared to non-users. This increased risk persisted even after adjusting for common stroke risk factors like obesity and migraines.
Combined hormonal contraceptives have long been known to carry a small risk of serious cardiovascular events, particularly ischemic stroke caused by blockage of blood flow to the brain. A recent large-scale study tracking over two million women further demonstrated that various forms of combined hormonal contraceptives—including pills, patches, vaginal rings, and certain intrauterine devices—elevate stroke risk. Notably, the vaginal ring was associated with a 2.4-fold increase in stroke risk and 3.8-fold increase in heart attack risk, while the contraceptive patch increased stroke risk nearly 3.5 times. In contrast, progestin-only contraceptives showed no increased risk for stroke or heart attack, suggesting oestrogen's key role in this risk elevation.
Role of Oestrogen in Stroke Risk
Combined contraceptives include synthetic forms of oestrogen (usually ethinylestradiol) and progestin. Natural oestrogen plays a part in normal blood clotting processes, but the synthetic oestrogen in contraceptives is more potent and administered at constant high levels. This leads to increased production of clotting proteins and suppression of natural anticoagulants by the liver, creating a greater tendency for dangerous blood clots to form.
Abnormal clot formation can obstruct arteries supplying the brain, causing ischemic stroke. The elevated clotting risk is enhanced in women who smoke, suffer migraines, or have genetic clotting predispositions. Additionally, oestrogen may influence blood vessel function and vascular tone over time, further contributing to stroke risk.
Balancing Risk and Awareness
Although these findings may raise concern, it is important to emphasize that the absolute risk of stroke related to combined hormonal contraceptive use remains low. Estimates suggest fewer than 40 cases per 100,000 women annually. However, given the widespread use of these contraceptives, even a small risk increase translates into a notable number of cases at the population level.
Many women continue using combined hormonal contraceptives because alternatives may be less effective, less accessible, or have their own drawbacks. Additionally, gaps in women-specific health research mean potential risks have often been under-recognized and inadequately communicated.
Women deserve comprehensive, evidence-based information to make informed choices about contraception. Importantly, pregnancy and the postpartum period carry higher stroke risks compared to contraceptive use, which provides additional context in evaluating these options.
Continued research is essential to better understand hormonal influences on female vascular health, expand safe contraceptive choices, and empower women with knowledge about the benefits and risks of each method.
