Women who take birth control pills are at an increased risk for ischemic stroke, a type of stroke triggered by blood clots, according to a new study published in the journal MedLink Neurology. The severity of the risk depends upon other health factors.
For healthy young women without any stroke risk factors, the risk of stroke associated with taking birth control pills is small. But in women with other stroke risk factors, “the risk seems higher and, in most cases, oral contraceptive use should be discouraged,” said researchers from Loyola University Medical Center and Loyola University Chicago Stritch School of Medicine.
Strokes linked to the use of oral contraceptives were first reported in 1962. Early versions of birth control pills contained doses of synthetic estrogen as high as 150 micrograms. Today, most birth control pills contain as little as 20 to 35 micrograms of synthetic estrogen, with none containing more than 50 micrograms.
Specifically, birth control pills increase the risk of ischemic strokes, which are caused by blood clots and account for about 85 percent of all strokes. In the general population, oral contraceptives do not appear to increase the risk of hemorrhagic strokes, which are caused by bleeding in the brain.
The prevalence for ischemic strokes is 4.4 strokes for every 100,000 women of childbearing age. Birth control pills increase the risk 1.9 times to 8.5 strokes per 100,000 women, according to a well-performed “meta-analysis” cited in the report. This is still a small risk, as 24,000 women would have to take birth control pills to cause one additional stroke, according to the report.
The risk for stroke is significantly higher, however, for women who take birth control pills and also smoke, have high blood pressure or have a history of migraine headaches. Women with these health risks should be discouraged from using oral contraceptives, the report said.
Furthermore, women who receive hormone replacement therapy with estrogen alone or combined with progesterone increase their risk of ischemic stroke by 40 percent. And the higher the dose, the higher the risk, the report said.
Worldwide, more than 100 million women have used oral contraceptives at some point in their lives. In the United States, there are about 40 brands of oral contraceptives and 21 brands of emergency contraceptive pills.
The report is an update of one originally published in Medlink Neurology in 2003.