Birth control pills increase risk of stroke in women with other risk factors

Researchers found a slight increase for all women on the pill, but much more for women already at risk of a stroke.

By Stephen Feller

MAYWOOD, Ill., Sept. 18 (UPI) -- Researchers found that birth control pills slightly increase the risk for having a stroke. The risk is comparatively weak for those with no other risk factors for stroke, but increases for women who already are at greater than normal risk for having one.

Previous research has linked increased risk for migraines, heart attack and stroke with using oral contraception, leading researchers to conduct a meta-analysis of studies because of what they call inconsistencies in method.


The new study, published in MedLink Neurology, is an update of a study conducted by researchers at Loyola University in 2003.

"When prescribing oral contraceptives, doctors should balance the risks and benefits for each individual patient," said Dr. Jose Biller, a researcher at Loyola University Health System, in a press release. "For a healthy young woman without any other stroke risk factors, the benefits of birth control pills probably outweigh the risks. But if a woman has other stroke risk factors, she should be discouraged from using oral contraceptives."

Overall, there are 4.4 ischemic strokes per 100,000 women of child-bearing age. Researchers found in their new analysis that birth control pills increase the risk of having a stroke by 1.9 times, which increases that average to 8.5 strokes per 100,000 women; or, one additional stroke for every 25,000 women who uses an oral contraceptive.


For women who take birth control and also smoke, have high blood pressure, or a history of migraines, researchers said the stroke risk is much higher. The study suggests these women should not be taking oral contraceptives.

Oral contraceptives do not appear to play a role hemorrhagic strokes, caused by bleeding on the brain, but have been shown somewhat consistently to play a role ischemic strokes, which are caused by blood clots. Roughty 85 percent of all strokes are caused by clots.

The first stroke connected to an oral contraceptive was reported in 1962, and the risk for stroke has been debated by researchers for most of the time since. At that time, the birth control pill included estrogen levels as high as 150 micrograms, whereas now they are between 20 and 35 micrograms, with none exceeding 50 micrograms per dose.

Around 100 million women use one of the 40 oral contraceptives or have used one of the 21 brands of emergency contraceptives on the market in the United States.

"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 said.


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