Summary: Oral contraceptives that contain estrogen only are more likely to cause serious blood clots in women than oral contraceptives containing estrogen and progestogen combinations.

Women who use oral contraceptives with estrogen and drospirenone, desogestrel or     gestodene are 6 times more likely to have serious blood clots when compared with non- users.

• According to a study recently published in the British Medical Journal, an extensive study has been conducted in order to assess the risk of venous thromboembolism (serious blood clots) in women who use oral contraceptives. For this study, data was taken from 4 different data registries in Denmark, and the compilation included non-pregnant Danish women ages 15-49 with no previous history of blood clots or cancer. The women were followed from January 2001 to December 2009. During the eight years of observation, out of a total of 8 million women, over 4,000 women experienced their first ever thromboembolic event. When compared with non-users of hormonal contraceptives, women who used contraceptives with levonorgestrel (estrogen plus progestogen formulation) had a 3-fold higher risk of venous thromboembolism. In contrast, women who used contraceptives with drospirenone, desogestrel, or gestodene (estrogen only formulations) had a 6-fold higher risk of venous thromboembolism than non-users. Researchers of this study noted that the increased risk remains even after taking into account other possible causes for venous thromboembolism. The risk of serious blood clots in users of these types of contraceptive formulations is about 10 per 10,000 women . This means that about 2,000 women should shift from using oral contraceptives with drospirenone, desogestrel, or gestodene to contraceptives with levonorgestrel to prevent one event of venous thromboembolism a year ¹

¹Risk of Venous Thromboembolism From Use of Oral Contraceptives Containing Different Progestogens and Oestrogen Doses: Danish Cohort Study, 2001-9, The British Medical Journal, 2011, pp. 1-15.