Despite repeated studies and claims from Bayer Healthcare that its birth control pills are safe, others argue that contraceptives like Yaz and Yasmin significantly increase the risk of blood clots and the potential dangers associated with them compared to other birth control pills.

At the times they were introduced, in 2001 and 2006 for Yasmin and Yaz respectively, the progestin they were made from was considered safer than other forms of progestin. However, studies published by the British Medical Journal have cast doubts on this interpretation of the results.

The first study examined blood clot risks in Danish women in good health, between ages 15 and 49. Of the more than 4,ooo blood clot cases the study examined, more than half were related to the use of oral contraceptives with contents similar to Yaz and Yasmin.

The second study involved more than 3,000 women in the Netherlands, and found that the progestin that is used in Bayer’s medications were more than six times as likely to be associated with blood clots than those women who took older contraceptives.

The consumer watchdog organization Public Citizen’s Health Research Group has already put Yasmin on its “do not use” list because of other risks, specifically raising blood potassium levels. The agency advocates using older drugs prior to third generation drugs such as Yasmin or Yaz, as they do not show such dangerous risks as the newer drugs.

The U.S. FDA is investigating the drugs with ongoing studies. As of last November, the FDA has reported 993 cases of pulmonary blood clots, 487 of deep vein clots, and 229 of other clots, all associated with these two medications. Over 1100 lawsuits have been filed pertaining to Yaz and Yasmin. Most of these are centered in a major suit filed in Southern Illinois. Bayer also has to contend with multiple class action suits claiming everything from economic loss to personal injury, including having been challenged in Canada.