CHICAGO, Oct. 26 (UPI) -- Oral contraceptives can nearly double the risk of stroke in women, a U.S. review of studies finds.
Dr. Jose Biller, Dr. Michael J. Schneck and Dr. Sarkis Morales-Vidal, all Loyola University Health System neurologists, say oral contraceptives used today contain much lower concentrations of estrogens than older preparations.
The review, published in MedLink Neurology, found there were about 4.4 ischemic strokes for every 100,000 women of childbearing age, but birth control pills increase the risk of stroke 1.9 times, to 8.5 strokes per 100,000 women.
However, for women who take birth control pills and also smoke, have high blood pressure or have a history of migraine headaches, the stroke risk was significantly higher.
How oral contraceptives may cause strokes is not completely understood, but two possible mechanisms are the increased risks of blood clots and high blood pressure associated with oral contraceptives, the study authors say.
"These observations obviously need to be considered in the proper context of a careful understanding of possible risks and benefits associated with the use of oral contraceptives, as well as those associated with other forms of contraception," Biller says in a statement.