Menstruation that does not go away for more than 7 days is called prolonged menstruation. Prolonged menstruation and endometrial thickening are commonly associated with diseases due to endometrial polyps, uterine fibroids, endometrial hyperplasia, and endometrial cancer. For women in their reproductive years, pregnancy-related diseases such as miscarriage, ectopic pregnancy and trophoblastic diseases should be ruled out first. 1. Endometrial polyps: caused by overgrowth of local endometrium, the number can be single or multiple, the size ranges from several millimeters to several centimeters, the clinical manifestations are mostly intermenstrual bleeding, excessive menstruation, prolonged menstruation or irregular bleeding. 2. Uterine fibroids: there is a close relationship between the location of uterine fibroids and the clinical manifestations of patients. Fibroids close to the endometrium may manifest as prolonged menstruation, increased menstruation, prolonged menstruation, drenching bleeding and shortening of menstrual cycle, and in severe cases, secondary anemia may occur. 3. Endometrial hyperplasia: non-physiological and non-invasive endometrial hyperplasia will lead to thickening and increase of endometrium, which often manifests as prolonged menstruation, heavier menstruation, or bleeding between menstrual periods. 4. Endometrial cancer: 90% of endometrial cancer patients have irregular vaginal bleeding, which usually occurs after menopause. For perimenopausal women, it can manifest as increased menstrual flow, prolonged menstruation, drenching menstruation, and bleeding between periods. Once prolonged menstruation occurs, it is recommended that gynecological outpatient consultation should be made as early as possible for clear diagnosis, early detection and early treatment to avoid serious complications.