Oral contraceptives are known to increase a woman’s risk of blood clots. Recent research shows, however, that the newer types of birth control pills containing the progestin drospirenone raise the risk much more than older types containing levonorgestrel. Epidemiologists found that women taking pills like Yasmin, Yaz or Ocella were two or three times more likely to experience a clot than those taking pills such as Jolessa, Seasonale or Seasonique.
These clots were not deadly, but they can be quite dangerous. When blood clots lodge in the legs they cause deep vein thrombosis. If those clots break loose and travel to the lungs they can cause pulmonary embolisms. Although the overall risk of such problems is low, otherwise healthy women should be informed about this potential danger from birth control pills.
[BMJ, online April 21, 2011]