During the menstrual period with a condom is also can not cohabit, because the cervical mucus plug has been menstrual blood washed away, this mucus plug can prevent the vaginal bacteria upstream infection, and the mouth of the uterus is open. If you have intercourse, it is easy to bring the amount of bacteria to the vagina to cause vaginitis, cervicitis, serious endometrial inflammation, bilateral tubal inflammation, and pelvic inflammatory disease, may also cause menstrual blood reflux, that is, menstrual blood can be through the bilateral tubes into the abdominal cavity, causing endometriosis. Because of the menstrual blood and a large number of endometrium, if the endometrium in the pelvic growth, it will cause pelvic adhesions, chronic pelvic pain, serious and also cause infertility, in the period of menstruation with a condom can not be cohabitation.