Women can’t have sex during menstruation for the following reasons: 1) The endometrium will be shed during menstruation, and a lot of blood will flow out, so if you have sex at this time, it will cause the endometrium to shed more, and the amount of menstrual blood will increase, which will easily lead to anemia in serious cases. 2) The endometrium of the uterus is traumatized due to the menstruation period and the cervix is in the open state, and blood is the best culture base for bacteria. 3) If you have sex during menstruation, it will easily lead to genital infection or upstream infection, which will affect fertility in serious cases. As the cervix is in an open state, blood is the best culture medium for bacteria, and sex during menstruation can easily lead to genital infection or upward infection causing pelvic inflammation, tubal inflammation and other diseases, which can seriously affect fertility.3. If you have sex during menstruation, the backflow of the menstrual blood due to the extrusion will easily cause the endometrium to enter the pelvic cavity, resulting in endometriosis. It is recommended that women avoid having sex during menstruation to avoid greater harm to the body, and it is recommended to have sex after menstruation.