For millions of women, combined hormonal contraceptives are a routine part of life, offering a reliable and convenient way to prevent pregnancy and regulate menstrual cycles. However, new research is highlighting a serious, often underestimated concern: the risk of stroke.
Data presented at the European Stroke Organisation Conference suggests that combined oral contraceptives—those containing both oestrogen and progestogen—may notably raise the risk of cryptogenic stroke. This type of stroke is sudden and lacks an identifiable cause.
Nearly 40% of Strokes in Young Adults Are Cryptogenic—Especially in Women—Highlighting Possible Sex-Specific Factors Like Hormonal Contraceptives, New Study Finds
Notably, cryptogenic strokes account for around 40% of all strokes in younger adults, especially women. This points to possible sex-specific factors, such as hormonal contraceptive use, that may contribute to the elevated risk—an idea supported by the recent findings.
At this year’s European Stroke Organisation Conference, researchers shared results from the Secreto study—an international effort aimed at uncovering the causes of unexplained strokes in young adults aged 18 to 49. The study included 608 patients from 13 European countries who had experienced cryptogenic ischaemic strokes.
One of the most significant findings was that women using combined oral contraceptives were three times more likely to suffer a cryptogenic stroke than those who didn’t use them. This increased risk remained even after accounting for other contributing factors such as obesity and migraines.
It’s already known that hormonal contraceptives containing both oestrogen and progestin carry a small but increased risk of serious health complications like ischaemic stroke, where a blockage disrupts blood flow to the brain.
Large-Scale Study Links Combined Hormonal Contraceptives to Increased Stroke and Heart Attack Risks in Women, with Vaginal Ring and Patch Showing Highest Risks
Further supporting these concerns, a large-scale study published earlier this year, which followed more than two million women, found that combined hormonal contraceptives—including pills, IUDs, patches, and vaginal rings—were linked to higher risks of both stroke and heart attack. Specifically, the vaginal ring raised stroke risk by 2.4 times and heart attack risk by 3.8 times, while the contraceptive patch increased stroke risk by nearly 3.5 times.
By contrast, a progestin-only IUD showed no increased risk for either condition, suggesting that oestrogen may be the primary factor behind these elevated risks. Although the absolute risk remains low—fewer than 40 out of every 100,000 women using combined hormonal contraceptives will experience a stroke—the global implications are substantial due to the widespread use of these contraceptives.
Combined hormonal contraceptives contain synthetic forms of the sex hormones oestrogen (typically ethinylestradiol) and a progestin, a man-made version of progestogen.
Synthetic Estrogen in Contraceptives Amplifies Blood Clotting by Increasing Clotting Proteins and Reducing Natural Anticoagulants
While natural oestrogen in the body helps promote blood clotting—an essential function for healing wounds and preventing excessive bleeding—the synthetic version used in contraceptives is more potent and delivered in consistent, higher doses. This triggers the liver to produce additional clotting proteins while reducing the body’s natural anticoagulants, shifting the balance toward easier clot formation.
Although this response helps reduce bleeding, it also increases the risk of developing abnormal clots, which can lead to serious conditions like stroke. This risk is further elevated in individuals who smoke, suffer from migraines, or have inherited clotting disorders.
If a clot forms in an artery supplying the brain—or travels there from another part of the body—it can block blood flow and trigger an ischaemic stroke, the most common form of stroke. Clots may also develop in deep veins, such as those in the legs or abdomen.
Beyond clotting, oestrogen can also cause slight increases in blood pressure and impact blood vessel function over time, contributing further to stroke risk.
Estrogen’s Clot-Promoting Effects May Underlie Increased Risk of Cryptogenic Stroke in Combined Hormonal Contraceptive Users
These clot-promoting effects of oestrogen may help explain the recent findings linking combined hormonal contraceptive use with a higher risk of cryptogenic stroke—a type of stroke with no clear cause, but which may be driven by subtle, underlying factors like hormone-related clotting.
These numbers may seem alarming, but the actual risk remains low. For instance, only one additional stroke is expected per 4,700 women using the combined pill each year.
While rare for individuals, this risk adds up globally, given how many women use these contraceptives—helping explain the high rate of cryptogenic strokes in younger women.
Many continue using them, either unaware of the risks or due to limited alternatives. This reflects a broader issue: women’s health research has long been underfunded and male-centered, leaving gaps in our understanding of how hormonal contraceptives affect women beyond birth control.
Women deserve clear, accurate information to make informed choices. While the stroke risk is small, it’s still higher during pregnancy and postpartum. With better research and communication, women can choose the option that best fits their needs and health.
Read the original article on: Science Alert
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