You should not have intercourse until two or three days after the end of your period, and not when your period has just ended. When the period has just ended, the opening of the uterus is still slightly open, so if you have sex at this time, you are prone to retrograde infection. If the infection is serious, it can lead to cervicitis, endometritis and pelvic inflammatory disease, which can seriously affect a woman’s health and can even affect pregnancy. Intercourse right after menstruation can also lead to endometriosis, as it is possible that the menstrual blood has not been completely drained yet, leading to retrograde flow of menstrual blood. From the above analysis, we can know that when menstruation has just ended, there may still be a small amount of menstrual blood not yet discharged and the uterine opening has not closed completely, so if you have sex at this time, it is most likely that infection and reflux of menstrual blood will occur, leading to endometriosis.