Yaz and Yasmin both use a new type of progestin hormone called drospirenone, which was designed to reduce many of the side effects of earlier birth control pills. However, researchers have now discovered that this chemical may contribute to more serious health risks.

In early FDA clinical trials, Yaz research identified risks with drospirenone, finding that the hormone could increase the level of potassium in the blood, leading to heart attacks and blood clots.

In August of 2009, The British Medical Journal published two independent studies conducted in Denmark and The Netherlands. Both found that women taking drugs like Yaz and Yasmin, with the hormone drospirenone, had higher risks for blood clots.

The British Medical Journal published further Yaz research in October of 2011 with a study from the University of Copenhagen finding that drugs like Yaz could increase the risk of venous blood clots.

FDA Blood Clots Risk Study

On October 27, 2011, the FDA released its own study of more than 800,000 women. Although it reached similar results, the FDA study quantified that drugs like Yaz containing drospirenone could actually increase the risk of blood clots by as much as 74%.

With such high occurrence rates and estimates that more than 80 million women have taken these birth control drugs, it came as little surprise when The Institute for Safe Medicine Practices reported that Yaz and Yasmin ranked second highest in 2011 for the number of complications reported to the FDA.

With Yaz research mounting and more than 10,000 lawsuits filed by women alleging serious side effects, Bayer announced in early 2012 that it would begin settling injury claims. The company has reserved more than $1 billion to settle these claims and continues to resolve cases for those affected.