Menstruation for more than 30 days may be caused by pregnancy-related diseases, endocrine disorders, uterine pathology, systemic diseases and other diseases. 1. Pregnancy-related diseases, such as preeclampsia, gravida and malignant gravida and other trophoblastic diseases can cause irregular vaginal bleeding, which can be clearly diagnosed by blood HCG test, gynecological ultrasound and other examinations. 2. Endocrine disorders, due to various reasons, the level of estrogen in the body is too low, when the level of estrogen in the body is not enough to support the uterine lining, the endometrium will fall off, thus irregular vaginal bleeding occurs. 3. Uterine lesions, endometrial cancer, cervical cancer, cervical polyps and other uterine lesions can also cause prolonged periods and other menstrual abnormalities. In this case, ultrasound or colposcopy of uterus and adnexa as well as histopathologic examination should be performed to confirm the diagnosis. 4. Systemic diseases, such as idiopathic thrombocytopenic purpura, coagulation disorders and other systemic diseases, can also cause excessive menstrual flow, prolonged menstrual period and other abnormal manifestations. After excluding reproductive system diseases, the disease can be considered. Bone marrow aspiration and related blood tests are usually sufficient for a clear diagnosis. Prolonged menstrual cycle should be taken seriously, and it is recommended to consult a doctor in time to identify the cause of the disease and actively treat the primary disease.