There are more reasons why menstruation comes once every two months at the age of 45, which may be caused by perimenopausal syndrome, polycystic ovary syndrome, cervical polyps, and other diseases such as endometrial polyps. 1. Perimenopausal syndrome: Perimenopausal syndrome is caused by the failure of ovarian function, and patients will experience menstrual disorders, hot flashes, dizziness, insomnia and other symptoms. So 45 years old patients with perimenopausal syndrome will have menstruation once every two months. 2. Polycystic ovary syndrome: the specific cause of polycystic ovary syndrome is not clear, the main symptoms of patients are irregular menstruation, scanty menstruation, hairy, acne and so on. Therefore, 45-year-old patients will have the performance of menstruation once every two months. 3. Cervical polyps: the etiology of cervical polyps is still unclear, and it is considered to be related to chronic inflammation of the cervix and abnormal response to elevated estrogen levels. Patients will appear bleeding between menstrual periods, bleeding after sexual intercourse, leukorrhea and other manifestations, so 45-year-old patients with cervical polyps may be manifested as menstruation once every two months. 4. Other diseases: 45-year-old patients appear menstruation once every two months, may also be endometrial polyps, endometritis and other diseases. If you are 45 years old and have the symptom of menstruation once every two months, you should go to the hospital in time to improve the relevant examination, under the guidance of the doctor to clarify the cause of the disease, and carry out targeted treatment.