As of mid-2013, new data have clarified the level of risk of venous and arterial thrombosis in women using oral contraception containing drospirenone, a progestin derived from spironolactone. Several studies showed a statistically significant, approximately twofold increase in the risk of venous thrombosis in women using oral contraception containing drospirenone, compared with women using second-generation oral contraceptives. Another study on arterial thrombosis showed a statistically significant increase in the number of strokes in women using contraceptives containing drospirenone combined with 30 microgram to 40 microgram of ethinylestradiol per tablet, compared with women not using contraception.