Under normal circumstances, you can smell the odor of blood during menstruation, but it should not be accompanied by other odors. If you smell a foul odor during menstruation, it may be due to an infection on the surface of a malignant tumor or mass in the reproductive tract, such as the shedding of a cancerous mass that causes hemorrhage, resulting in a foul odor. Some women have endometrial polyps that are infected, which can also cause this phenomenon. When this happens, we must do routine gynecological examinations and pelvic ultrasound to see if there are any abnormal masses in the uterine cavity, in the vagina, or on the cervix. Sometimes we also need to do a biopsy on the mass and send it for pathology to rule out malignant lesions, so that malignant tumors can be detected and treated as early as possible.