The normal menstrual cycle is 21-35 days, the period lasts 2-7 days, and the average blood loss is 20-60 ml. Anything that does not meet the above criteria is abnormal uterine bleeding, which is one of the most common gynecological problems in women of childbearing age. There are many causes of abnormal uterine bleeding, the common causes are as follows: 1. Endometrial polyps: some patients can be asymptomatic, those with symptoms can show bleeding between periods, excessive menstruation or irregular bleeding, which can also cause infertility. High risk factors for endometrial polyps include advanced age, late menopause, obesity, diabetes, hypertension, etc. 2.Uterine adenomyosis: Patients show dysmenorrhea, heavy menstruation and prolonged periods, which are caused by the invasion of the endometrium of the basal layer into the myometrium of the uterine wall, with multiple pregnancies and deliveries, abortions, chronic endometritis, etc. resulting in damage to the basal layer of the endometrium. 3.Uterine fibroids: Patients show increased menstrual flow, prolonged periods or irregular vaginal bleeding, in addition to increased leucorrhea, lower abdominal masses, bladder pressure symptoms, and anal swelling sensation. The specific cause is unknown and may be related to female sex hormone levels. 4.Atypical endometrial hyperplasia: It is a precancerous lesion of endometrial cancer, which can develop into endometrial cancer if not treated. It is mainly caused by long-term stimulation of endometrium by single estrogen, which can be seen in patients with anovulation, obesity, endocrine functional tumor and long-term use of tamoxifen drugs. 5.Dysfunctional uterine bleeding: Patients show a variety of irregular uterine bleeding, such as disorder of menstrual cycle, variable length of menstrual period, variable or increased menstrual volume. It is mainly due to the dysfunction of the reproductive endocrine axis and can be seen when the female organism is affected by various internal and external factors, such as mental tension, malnutrition, metabolic disorders, chronic diseases, sudden environmental and climatic changes, dietary disorders, excessive exercise, alcoholism, etc. 6.Tumors of reproductive organs: such as ovarian tumors, vaginal tumors, endometrial cancer, cervical cancer, etc. can also cause abnormal uterine bleeding. As mentioned above, there are various causes of abnormal uterine bleeding, which can cause infertility and anemia in serious cases, so patients need to consult a doctor in time to clarify the cause.