The abnormal uterine bleeding is a disease of the female reproductive endocrine system, and the brownish color inside the leucorrhoea before menstruation indicates poor luteal function. Normal uterine bleeding is menstruation, menstrual blood is generally dark red, in addition to blood, menstrual blood also contains endometrial debris and cervical mucus, in normal circumstances before the menstruation will not have brown in the leucorrhea this situation. The entire menstrual cycle is divided into proliferative phase, secretory phase and menstrual phase. Before menstruation, the endometrium is transformed by the luteal function, and endometrial exfoliation occurs. After the endometrium is exfoliated, it is discharged through the vagina together with blood, which is the menstrual period. When the luteal function is not good, it will prevent the endometrial lining from exfoliating and there will be a brownish discharge in the leucorrhoea before menstruation. At this time, you should go to the hospital for a gynecological ultrasound and hormone 6 test to understand the basic condition of the patient. There are also special circumstances that can cause brownish discharge before menstruation, such as women who have an intrauterine device placed.