Compared to women who did not use birth control pills, the clot risk was three times higher among those who used pills with levonorgestrel, and six times higher among those who took pills with drospirenone, desogestrel or gestodene.
But the absolute risk of blood clots associated with the newer pills remained relatively low, about 10 per 10,000 women, according to the University of Copenhagen researchers.
The American College of Obstetricians and Gynecologists has more about birth control pills.
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