Objective: Review the knowledge about changes in hemostatic system in combined oral contraceptives users (focused on studies published between 1997 and 2000). Type of study: Review of literature. Setting: Department of Clinical Hematology, University Hospital Hradec Králové, Czech Republic. Methods: Summary of the results of substantial studies published on this topic. Studies were identified by Medline database search. Results: Hemostatic changes were described in all subsystems (in both procoagulant and fibrinolytic system, in natural inhibitors of coagulation) and could be seen also in molecular markes of coagulation and fibrinolysis activity. Substantial differences were not described for ethinylestradiol doses 20-50 mg and up to 1997 also not for different progestins. More expressed acquired resistance to activated protein C at 3rd generation progestins in comparison with levonorgestrel was described recently as well as greater inhibition of fibrinolysis at desogestrel users. Conclusion: The results of recent studies indicate the differences in hemostatic changes between users of 3rd generation progestins, respective desogestrel, and users of levonorgestrel. However, the practical recommendations (aiming at minimalization of VTE risk) are focused on personal and family history and on patient counseling. The choice of progestin could be important but it is not cruicial.

        Key words: combined oral contraceptives, venous thromboembolism