Great aunt refers to menstruation. The fact that menstruation comes back after three days may be caused by endocrine abnormalities, medication factors, cervical factors and so on. 1. Endocrine abnormality: Women will affect the endocrine level in their body due to stress, external environmental changes, diet and other factors, if the endocrine abnormality occurs, it will lead to abnormal menstruation and abnormal vaginal bleeding. 2. Drug factors: women use hormonal drugs such as birth control pills, which will affect the level of hormones in the body, leading to menstrual disorders. 3. Cervical factors: women with polyps on the cervix, or cervical diseases such as cervical cancer, may experience bleeding from the lesion site, leading to abnormal vaginal bleeding. After three days of menstruation, you need to go to the hospital for sex hormone, ultrasound, gynecological examination and other tests to clarify the cause of the disease and target treatment.