There are the following reasons why you can’t have sex during menstruation: 1, during menstruation due to the accumulation of blood in the vagina discharged from the uterine cavity, the cervical opening is open to the presence of menstrual blood in the vagina. When you have sex, the bacteria in the vagina can enter the uterine cavity through the cervical opening, and women may experience uterine infection and pelvic inflammatory disease.2. When women have sex, the uterus will undergo strong contractions, which will cause the detached endometrium to ectopic into the pelvic cavity or into the uterine muscle layer. This can lead to endometriosis, dysmenorrhea, menstrual disorders, and even infertility.3. During menstruation, a woman’s body is more tired, and when she has sex, the woman may be more tired, so it is not conducive to the health of the body. During menstruation, women should pay attention to proper rest, keep the vulva clean and hygienic, and eat more nutritious food in favor of the body’s early recovery.