Objective: This study was undertaken to evaluate the effects on hemostatic factors of a low-dose preparation of levonorgestrel and ethinyl estradiol in a 12-cycle study.
Study design: Thirty healthy women began taking 100 microg levonorgestrel and 20 microg ethinyl estradiol on the first day of the menstrual cycle, continued to take the preparation for the next 21 days, and then took placebo for 7 days. Mean changes in prothrombin time, partial thromboplastin time, and levels of factors VII and X, antithrombin, plasminogen, fibrinogen, protein S, thrombin-antithrombin complexes, and D-dimer were analyzed at baseline and at cycles 3, 6, and 12 with paired Student t tests.
Results: Factor X, plasminogen antigen and activity, and D-dimer levels were significantly increased (P </=.01) during all 3 cycle periods. Antithrombin antigen and protein S total antigen levels were significantly (P </=.001 ) decreased at cycles 3, 6, and 12, whereas factor VII and protein S activity levels were significantly (P </=.05) decreased at cycle 3 and at cycles 3 and 6, respectively.
Conclusion: The effects on hemostatic factors in healthy women of a monophasic preparation of 100 microg levonorgestrel and 20 microg ethinyl estradiol were similar to those of other low-dose oral contraceptives.