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