The main reason is that menstruation is caused by the shedding of the endometrium and the relative relaxation of the endometrium. If you have intercourse at this time, it is likely that pathogenic bacteria will enter the uterine cavity along with the endometrium, which will clinically lead to inflammation of the endometrium, and may even seriously lead to inflammation of the pelvis. In addition, intercourse during menstruation may cause contraction of the uterus under the stimulation of intercourse, which may lead to the accumulation of blood in the uterine cavity into the pelvis and cause endometriosis, so do not have intercourse during menstruation. In addition, the menstrual period will have a certain pressure on women’s psychology, if they often have intercourse during the menstrual period, it is likely to lead to the symptoms of sexual frigidity, so do not have intercourse during the menstrual period.