The U.S. Food and Drug Administration (FDA) has completed its review of recent observational (epidemiologic) studies regarding the risk of blood clots in women taking drospirenone-containing birth control pills. Drospirenone is a synthetic version of the female hormone, progesterone, also referred to as a progestin. Based on this review, FDA has concluded that drospirenone-containing birth control pills may be associated with a higher risk for blood clots than other progestin-containing pills.