Two studies published in the British Medical Journal have found that certain new birth control medications such as Yaz, Yasmin and Ocella could double or triple a woman’s risk of blood clots. Two trials involving American and British women found that women taking newer, so-called ‘fourth generation’ contraceptives that contain drospirenone were at a two to three times higher risk of developing blood clots than females who took older birth control products that contain levonorgestrel.
While the absolute risk of developing a blood clot on the newer birth control products is still relatively small – approximately 31 per 100,000 women compared with 12.5 per 100,000 in the control group – there is still an increased risk. Bayer AG, who manufactures and markets Yaz and Yasmin, believes the new studies do not change the overall safety of the drugs.
Oral birth control medications contain a combination of estrogen and progestin, with progestin being the strongest agent in the mix. Estrogen is added to offset some of the side effects of progestin. While previous studies found that estrogen increased some women’s risk for blood clots, other studies suggested that progestin could too.
While the BMJ studies are open to interpretation as to the actual risk of blood clots faced by users, doctors need to continue to inform their patients about any potential risk from any form of birth control medication. Women who are overweight, older than 35 and smoke or who have a history of blood clots should avoid oral contraceptives if at all possible.