There are many reasons why a woman’s menstruation is not normal, and the common causes are pregnancy, medication factors, mental factors, tumors, polycystic ovary syndrome and so on. 1. Pregnancy: Women of childbearing age with a history of sexual intercourse in the last two weeks, who usually have normal menstrual periods, may be pregnant if they suddenly experience abnormalities. 2. Drug factors: long-term use of contraceptive pills to avoid unwanted pregnancy, but contraceptive pills for women’s body itself is harmful, can cause irregular menstruation. 3. Mental factors: long-term mental tension, excessive pressure, environmental changes, etc., affecting the ovaries, can lead to abnormal menstruation. 4. Tumor: Ovarian tumor of secretion function, pituitary microadenoma, etc., lead to abnormal menstruation, delayed menstruation or no menstruation irregularities; uterine fibroids, especially submucosal uterine fibroids, lead to abnormal hemorrhage from the uterine cavity, causing shortening of menstrual cycle and increase in the amount of blood. 5. Polycystic Ovary Syndrome (PCOS): due to endocrine abnormality, the menstrual cycle becomes long and abnormal. 6. Pelvic inflammatory disease: patients with pelvic inflammatory disease have abnormal menstruation and increased menstrual flow. There are other possible causes of abnormal menstruation, such as abnormal luteal function, it is recommended to go to the Obstetrics and Gynecology clinic of the hospital in time to clarify the cause of the disease, under the guidance of a professional physician, and follow the doctor’s instructions for treatment, do not use your own medication, so as not to delay the condition.