Study Examines Birth Control Pill Stroke Risk

C H I C A G O, July 5, 2000 -- A new report suggests that while women takingbirth control pills — even the newer, low-dose forms — are athigher risk of stroke, that risk is outweighed by the contraceptivebenefits of the pills.

The report, an analysis of 16 previous studies, is intoday’s Journal of the American Medical Association.

The low-dose forms, taken by most of the more than 10 millionU.S. women using oral contraceptives, contain less estrogen thanthe pill introduced 40 years ago and are thought to be safer.Still, women taking them were nearly twice as likely as non-usersto suffer a stroke, while women using higher-dose pills facednearly a threefold risk.

However, since strokes are so rare in women of reproductive age,the risk translates to only one additional stroke yearly per 24,000women for low-dose pill users and one per 12,000 women for higherdosages, the report concludes.

Measuring Risk

The risks were associated with current rather than previous use.

Strokes are a known risk factor for higher-dose pills butprevious research had been less clear about lower dosages — pillswith less than 50 micrograms of estrogen, said Dr. S. ClaiborneJohnston, a co-author of the report and assistant professor ofneurology at the University of California at San Francisco.

“The key is about whether this risk matters,” given howeffective the pill is at preventing pregnancy, Johnston said.

If oral contraceptives were replaced by condoms, an estimated687,000 additional unintended pregnancies would result each year,the study authors said. Some of those women likely would haveabortions, and those who didn’t would face health risks associatedwith pregnancy plus “major psychological and economicconsequences” of unintended children, Johnston said.

Stroke risk linked to the pill thus appears to be outweighed byits benefits, the authors wrote.

The study was funded by the National Stroke Association and theNational Institutes of Health.

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