Clotting factors after emergency contraception

Abstract

Women with a previous history of thromboembolic disease have often been denied oral emergency contraception because of a theoretical concern about increasing their risk of thrombosis.

Methods: Eleven healthy volunteers with regular periods were recruited to the study. A thrombophilia screen was done at the first visit and they each had four measurements of Factor VII and antithrombin III taken at mid-cycle for two cycles. In the third cycle, emergency contraception was given mid-cycle and blood samples were taken 1, 3 and 7 days later. A further four samples were taken during the following cycle and, where the cycle had been significantly foreshortened due to the emergency contraception, a fifth cycle was monitored. The treatment given during the third cycle was the standard Yuzpe regimen of emergency contraception, which consists of 100 micrograms of ethinylestradiol and 500 micrograms of levonorgestrel repeated after twelve hours.

Results: There was a wide inter- and intra-subject variation in clotting factors in the observation months. There was no obvious effect noted in the levels of the factors measured after treatment, either in the first week or in the subsequent month(s) of follow-up.

Conclusions: The dosage of ethinylestradiol used in emergency contraception is very shortlived and this study shows no effect on clotting factors. This suggests that ethinylestradiol should not be automatically dismissed in women with previous thromboembolic disease.