Wearing a condom during menstruation is also not allowed, because during menstruation the uterine opening is open, even if wearing a condom, it may lead to the invasion of pathogenic bacteria, causing cervicitis or inflammation of the endometrium. In addition, during menstruation, there is menstrual blood in the uterine cavity. If you have intercourse, under external stimulation, especially when you reach orgasm, which causes sexual excitement, the uterus will contract and may cause menstrual blood to enter the pelvic cavity along the fallopian tubes. When the menstrual blood has shed endometrium, it may cause endometriosis, which can cause recurrent menstrual cramps and infertility in about 50% of patients, so you should not have intercourse during menstruation even if you wear a condom.