Oral contraceptives, i.e. birth control pills, increase the risk of stroke for women, most significantly for women who also have other stroke risk factors. Scientists examining this connection want to increase awareness so that women taking or thinking about taking birth control understand the potential consequences.
First, researchers stress that the increased risk of stroke from birth control pills is minimal for women who don’t also have other risk factors for stroke. Additionally, the increased risk of stroke associated with birth control is for ischemic stroke, as opposed to hemorrhagic stroke.
Ischemic stroke, which is responsible for a large majority (87 percent) of all stroke cases, takes place when a blood vessel that supplies the brain with blood, carrying oxygen and nutrients, is blocked due to a blood clot. Hemorrhagic stroke, on the other hand, is the result of a ruptured blood vessel, as in an aneurysm. A third type of stroke is less severe, called a “transient ischemic attack” (TIA). These “mini-strokes” are caused by a temporary blood clot.
Why does taking birth control pills increase the risk of ischemic stroke? Researchers say that it increases an individual’s blood pressure and enhances the likelihood that blood will clot. Physicians can minimize the risk of stroke for women taking birth control pills by carefully considering the type and dose of estrogen and progestin in the medications they prescribe as well as the route of administration, which can vary from pill to patch.
"The ideal drug is one with the lowest estrogen and progestin doses that will be effective in preventing pregnancy while minimizing adverse effects," explained Sarkis Morales-Vidal, MD, and Jose Biller, MD.
They add that for women with risk factors for stroke, like high blood pressure, smoking habits, and migraine headaches, “oral contraceptive use should be discouraged.”
The connection between migraines and risk of stroke is still not very well understood. Scientists do know that a specific type of migraine is the focus, those with sensory disturbances or “aura,” where the afflicted person experiences flashes of light and tingling in the hands and face. A 2009 review of studies on migraine and stroke risk showed that the relative risk of stroke was much higher in people with migraines compared to people without migraines.
Researchers from the study hope that the new information could help inform women whose doctors do not tell them about their risk of stroke. Researchers say that only 15 percent of women with at least one risk factor for stroke are told by a medical professional to not begin taking birth control, and only 36 percent of at-risk women already taking birth control are told to stop.
In the words of Morales and Biller, “these findings highlight the need to improve physician counseling and patient compliance.”
The present study was published in the journal MedLink Neurology.