THURSDAY, Feb. 7, 2002 (HealthDayNews) -- Despite lower levels of estrogen, the new generations of birth control pills double the risk of stroke for women who take them, a new study shows.
In the first look at the risk of ischemic strokes from the latest generation of oral contraceptives, Dutch researchers say the newest pills are no safer than the older versions when it comes to clotting problems. In fact, they argue, the third-generation pills may be more dangerous than the second-generation ones.
The history of oral contraceptives has been one of trial and error.
The first generation of pills, introduced in 1960, was a mix of high doses of estrogen and one of two other hormones, lynestrenol or norethisterone, also known as progestogens. However, they increased the risk of clotting, which can lead to ischemic stroke. The next version, released in the 1970s, contained markedly less estrogen and only the progestogen levonorgestrel.
This combination also raised the risk of stroke, especially in smokers and women with high blood pressure. In addition, women complained of side effects from levonorgestrel, including acne, cholesterol problems and weight gain.
Hoping for the best, pill makers issued yet another formula in the 1980s that combined low estrogen levels with the less harsh progestogens desogestrel or gestodene.
Third-generation birth control pills haven't been used in the United States long enough to monitor women most at risk for stroke. However, Europe approved them sooner, letting researchers there compare risks among all three kinds of pills.
A team led by Jeanet M. Kemmeren, an epidemiologist at University Medical Center in Utrecht, looked for a link between oral contraceptives and ischemic strokes in nearly 1,130 women, aged 18 to 49, of whom 203 had suffered one such attack.
Women who reported using any oral birth control had a 2.3-times higher risk of stroke than those who never took the pill did, the scientists say. The risk with first-generation pills rose 1.7 times, compared with 2.4 and 2.2 times for the second- and third-generation incarnations, respectively.
As expected, smoking and high blood pressure aggravated the risk of ischemic stroke, say the researchers, who will present their findings today at a meeting in San Antonio of the American Stroke Association.
Kemmeren says that while the study shows the newer birth control pills aren't safer than the older variety, women don't need to be concerned about using them.
"The absolute risks are very low. I don't think women should be very worried," she says. Roughly three in 10,000 women suffer ischemic strokes, a rate that rises to six in 10,000 among those taking oral contraceptives.
However, if women shouldn't base their choice of oral contraceptive on stroke risk, Kemmeren's group says they should decide based on another complication: leg clots, or deep venous thrombosis.
In previous research, the scientists found women taking the third-generation pills were more likely than those on the second-generation ones to develop these clots. Although usually harmless, deep venous clots can migrate to the lungs and become deadly.
The Dutch team recommends women starting out on birth control opt for the second-generation pills.
Still, Stephen M. Schwartz, a University of Washington epidemiologist who has studied the link between strokes and birth control pills, says the latest findings should be "generally reassuring" for women.
However, he adds, the study didn't look at whether newer pills are more likely to cause hemorrhagic, or bleeding, strokes, which are the most common form of stroke in women of childbearing age.
What To Do
More than 10 million American women use oral contraception. For more on the pill, try the National Institutes of Health or the Feminist Women's Health Center.
For more on other forms of contraception, try Planned Parenthood.
