An updated report in MedLink Neurology stated that oral contraceptives are associated with a small but significant increase in ischemic stroke risk, particularly for women who smoke, have hypertension, or a history of migraine headaches.

Prior research has attempted to estimate the risk of stroke with oral contraceptive use, but inconsistency in formulations of oral contraceptives and a variations in stroke subtypes evaluated has led to diverse results. Strokes were first linked to oral contraceptives in 1962 and many formulas at that time contained synthetic estrogen doses of up to 150mcg; most now contain as little as 25–35 mcg. No commercially available oral contraceptives in the United States contain >50mcg of synthetic estrogen.

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In an update to a report originally published in 2003, Marisa McGinley, DO, from the Loyola University Medical Center, and colleagues reviewed recent studies on oral contraceptives, types of stroke, and other factors influencing stroke risk. Oral contraceptives appeared to increase the risk of ischemic stroke but did not appear to increase the risk of hemorrhagic strokes. However, this is still a small risk, as the report noted that 24,000 women would have to take birth control pills to cause one additional stroke.

The stroke risk was significantly higher among women taking oral contraceptives who smoke, have hypertension, or have a history of migraine headaches. Women with these stroke factors should be discouraged from taking oral contraceptives, the authors concluded.

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