A single-center, open-label, crossover, randomized study to investigate the impact of the transdermal contraceptive patch containing 0.55 mg ethinylestradiol and 2.1 mg gestogene (material no. 80876395) in a 21-day regimen as compared to a monophasic contraceptive containing ethinyestradiol and levonogestrel (0.33 mg/0.15 mg) in a 21-day regimen on hemostatic parameters in 30 women aged 18-35 years over 3 treatment cycles in each period