It may be normal for menstruation to become heavy once in a while, and it can’t be ruled out that it may be caused by uterine fibroids, adenomyosis, endometrial polyps, placement of intrauterine device, or spontaneous abortion. Normally, menstruation is small, suddenly menstruation becomes more than once by chance may also be normal, normal menstrual flow in 20-60ml, more than 80ml for menstruation, if only a mild increase in 7 days within the bleeding is completely clean without any other obvious discomfort, it may also be a normal phenomenon. 1. Uterine fibroids: the most common type of fibroids is large submucosal or intermural fibroids, which cause increased menstrual flow and prolonged menstrual period due to the enlargement of the uterine cavity, increase of endometrial area, and congestion and expansion of the venous plexus of the endometrium. The diagnosis can be assisted by history, physical examination and ultrasonography. 2. Adenomyosis: It is also due to the increase in endometrial area, endometrial hyperplasia, etc., which causes excessive menstrual flow, prolonged menstrual period, and secondary dysmenorrhea which is progressively aggravated. The diagnosis can be assisted by history, physical examination and ultrasonography. 3. Placement of intrauterine device (IUD): the stimulating effect of IUD on the endometrium after placement may also cause symptoms such as increased menstrual flow, prolonged menstrual period, or dribbling bleeding, etc. Diagnosis can be made by history and ultrasonography. 4. Spontaneous abortion: it can also cause increased vaginal bleeding, accompanied by outflow of embryonic tissues and obvious pain in the lower abdomen, etc. It can be diagnosed with the help of medical history, blood human chorionic gonadotropin and ultrasonography. There may also be other reasons for the sudden increase in menstruation, so it is recommended that you seek medical attention to rule out any abnormalities, and if necessary, standardize treatment under the guidance of your physician.