The purpose of this study is decrease of thrombosis risk in women that use combined oral contraceptives containing 20 mcg ethinylestradiol/3 mg drospirenone, 30 mcg ethinylestradiol/3 mg drospirenone, 35 mcg ethinylestradiol/2mg cyproterone acetate. Half of the women of each arm (group) receive only combined oral contraceptives (COC), other women receive combined oral contraceptives and antioxidant complex Selmevit.