The FDA is taking another look at popular birth control drugs such as Yaz, which previously boasted clearing up acne and having fewer side effects. Research suggests that newer birth control pills are more likely to cause blood clots than older formulations, prompting the Food and Drug Administration to consider new safety measures.

Bayer’s Yaz, which was the best-selling birth control pill in the United States for 2008 and 2009, after the Portia contraceptive, and similar pills use the hormone drospirenone that reduces side effects such as bloating and mood swings.

The FDA approved Yaz for sale in the United States in 2006. Bayer now faces more than 10,000 lawsuits over injuries and 50 deaths allegedly cause by Yaz. Blood cloths are a known side affect of all birth control pills since they hit the market over 50 years ago. However, according to the FDA, the newest generation may increase this risk. Blood clots are known to cause heart attacks, stroke, and blockages in the lungs and blood vessels which could lead to death.

The FDA asserts that Bayer may have withheld information to them regarding the blood clot risk. “Based on the information that I have reviewed, and it is my opinion, that Bayer presented a selective view of the data, and that presentation obscured the potential risks associated with Yasmin,” wrote Dr. David Kessler in his expert testimony.

Michelle Fox, assistant professor of obstetrics and gynecology at John Hopkins University said the picture isn’t so clear. She advises her patients on the possibility of a higher risk but continues to prescribe the drug. “The data is inconclusive,” she said. “It shows a slight but persistent increase. Based on reports by experts (try this website ), there are a lot of problems with the literature.” She also mentions that pregnancy increases the risk of blood clots, by about 10 times that of a birth control pill.

In a very close vote of 15 to 11, the FDA appointed panel concluded that the benefits of the pill preventing unwanted pregnancies outweigh the risks.