A woman should never have intercourse during her menstrual period, even with a condom. On the fifth day of menstruation, you cannot have intercourse with a condom if your period is not completely clean. The possible hazards of intercourse during menstruation include: during menstruation, the uterus and pelvic tissues of women are obviously congested, intercourse during menstruation will increase local tissue congestion and cause obvious symptoms of back pain. Intercourse during menstruation can easily cause the shed endometrium to be squeezed into the myometrium under the stimulation of external force, causing endometriosis. Intercourse during menstruation may also lead to the production of anti-sperm antibodies in both men and women, and anti-endometrial antibodies in women, causing immune infertility.