Despite lower levels of estrogen, the new generations of birth control pills double the risk of stroke for women who take them. Researchers say the newest pills are no safer than the older versions when it comes to clotting problems. In fact, the third-generation pills may be more dangerous than the second-generation ones.
The first generation pills, introduced in 1960, was a mix of high doses of estrogen and one of two other hormones, lynestrenol or norethisterone. 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 US 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.
In previous research, the scientists found women taking the third-generation pills were more likely to develop these clots than those on the second-generation ones. Although usually harmless, deep venous clots can migrate to the lungs and become deadly. However, 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.