You can’t have sex when you have your period because sex is prohibited during menstruation. Firstly, the endometrium is necrotic and shedding during menstruation, the cervical opening is slightly dilated, which facilitates the discharge of menstrual blood, and intercourse is prone to cause pathogenic microorganisms such as bacteria to multiply into the blood via the cervical opening up to the endometrial shedding wound, leading to systemic infection. Secondly, intercourse during menstruation is likely to cause contraction of the uterus, so that the shed endometrium and blood clots are extruded into the pelvis, leading to endometriosis, dysmenorrhea and secondary infertility. In addition, intercourse during menstruation is also likely to cause increased menstrual flow and prolonged periods. It is recommended not to have intercourse during menstruation to avoid losing a lot of money for a small reason. If you have intercourse inadvertently, it is recommended to consult a doctor promptly if there is any discomfort. If there is no obvious discomfort, you can observe the situation temporarily and pay attention to the volume, period and dysmenorrhea of menstruation.