Early menstruation after coitus may be caused by improper coitus operation, cervical erosion, endocrine disorders and other factors. 1. Improper operation of coitus: due to improper coitus strength or improper position, the endometrium is peeled off in advance, so the phenomenon of early menstruation occurs. 2. Cervical erosion: when a woman suffers from cervical erosion, the contact of coitus causes the local mucous membrane to break down and bleed, accompanied by pain in the lower abdomen, abnormal vaginal discharge and other symptoms, which is mistaken for early menstruation. 3. Endocrine disorders: due to too intense or frequent coitus, resulting in female endocrine disorders and affect the menstrual cycle, thus the phenomenon of early menstruation. Clinically, when vaginal bleeding occurs after intercourse, it is necessary to go to the hospital in time to see a doctor for a clear diagnosis and standardized treatment under the guidance of the doctor.