Abstract: Unscheduled bleeding is a common cause of discontinuation during the using of combined oral contraceptives(COC). Compliance can be improved by appropriate counseling about the possibility of unscheduled bleeding, as well as by the necessary prevention and treatment. The mechanisms underlying this kind of bleeding are not fully understood. There is little high-level evidence of clinical strategies to support the management of unscheduled bleeding associated with COC. It is critical to role out gynecological pathology for patients with persistent or new-onset unscheduled bleeding.