Abstract: There are three kinds of progesterone only contraceptives（POCs）， intramuscular injection， implants and levonorgestrel-intrauterine system（LNG-IUS）. POCs offer the safe，effective and reversible contraceptive options，particulary for women with the risk of venous thromboembolism. Breakthrough or irregular bleeding （BTB） and amenorrhea are the main side-effects，which often lead to discontinuation. The exact pathophysiological mechanisms of BTB remain unclear，but they are likely to relate to the chronic endometritis，thin and dilated wall of vessels in subendometrium，high expression of COX-2 and MMP-9. Many effective methods are tried to stop bleeding. The most important thing is to consult the women carefully before their utilization of POCs.

Key words: Contraception, Progestins, Metrorrhagia, Amenorrhea, Treatment