The 20-day period with blood clots can be considered abnormal uterine bleeding, the specific causes are related to endocrine disorders, coagulation dysfunction, uterine organic lesions, uterine diverticulum and so on. 1. Endocrine disorders: excessive obesity, long-term use of drugs, mental stress, hypothalamus-pituitary-ovarian function abnormalities and other factors easily lead to endocrine disorders. Then there will be irregular ovulation, and fluctuation of estrogen and progesterone levels, which will lead to abnormal shedding of endometrium, and then there will be irregular bleeding, and there will be blood clots when there is a lot of bleeding. 2. Abnormal coagulation function: patients with abnormal blood vessel wall, coagulation factor deficiency, thrombocytopenia and other diseases can also lead to prolonged menstrual bleeding, increased menstrual bleeding, blood clots and other symptoms. 3. Organic uterine lesions: patients with uterine smooth muscle tumors, adenomyosis, endometrial polyps and other structural changes are prone to abnormal uterine bleeding, which can also lead to postmenstrual bleeding and blood clots. 4. Diverticulum of the uterus: if the patient has a history of cesarean section, it is easy to form a scar diverticulum in the lower part of the uterus; the endometrial lining shed during menstruation and menstrual blood of this kind of patients are easy to accumulate in the diverticulum, which will lead to prolonged menstruation and the symptom of blood clots. In addition, endometrial inflammation, endometrial cancer, etc. can also cause unclean menstruation and other symptoms. It is recommended that patients go to the gynecology department of regular hospitals in time, receive relevant examinations, clarify the cause of the disease, and then follow the doctor’s instructions to receive treatment, so as to avoid delays in the condition.