The US Food and Drug Administration is looking into the risk of venous thromboembolism in women who use birth control pills that contain drospirenone, notably Bayer's Yasmin and Yaz products.

The agency said it is conducting the review following two recently-published studies in the BMJ which looked at whether there is a higher risk of blood clots in women taking pills containing the progestin drospirenone compared to a different progestin, levonorgestrel. These two new studies claimed the risk of VTE associated with Yasmin and Yaz is up to two to three times greater.

The FDA notes that other data have not reported an increase in risk, so the agency is "currently evaluating the conflicting results from these studies and will look at all currently available information to fully assess the risks and benefits of drospirenone-containing birth control pills".

Bayer says that its "analysis of the overall body of available scientific evidence continues to support its current assessment about the safety of its oral contraceptives". The German drugmaker adds that the risk of developing VTE using its drospirenone-containing pills is comparable to other birth control drugs and "this assessment is supported by consistent clinical findings over a 15-year period and up to 10 years of post-marketing study results".

The Leverkusen-headquartered firm added that it conducts ongoing monitoring of post-marketing surveillance data for all of its products and "will continue to work closely with the FDA on this matter".