In the menstrual period when intercourse may lead to infertility occurs, mainly in the menstrual period, due to the endometrium is shedding, the cervical mucosa is relatively speaking, resistance is relatively low, so if intercourse, is likely to bring in pathogenic bacteria, so that the cervical mucosa occurs in chronic inflammatory reaction. When the cervical mucosa has chronic inflammation there will be a large number of white blood cells, white blood cells will phagocytosis of sperm, so clinically it will lead to the possibility of infertility. In addition, if you have sex during the menstrual period, because the endometrium is in the state of peeling, so the pathogenic bacteria are also easily infected to the endometrium, in the clinic will cause inflammation of the endometrium or cause inflammation of the fallopian tubes, pelvic inflammation and lead to fallopian tube adhesion, in the clinic will also cause infertility, so in the menstrual period can not have sex.