It is not recommended to have sex just one day after menstruation, but since the fact of having sex has already happened, there is no need to be too nervous. Pay more attention to observe whether vaginal bleeding occurs again and whether there is abdominal pain. If the above abnormal symptoms occur, pay more attention to rest and take metronidazole, levofloxacin hydrochloride and other drugs to prevent infection. At the same time, drink more water and pay attention to washing the vulva to avoid prolonged bleeding that may lead to a decrease in body resistance and other diseases. In general, a day after the menstrual period is not really over, the uterus has not fully recovered, the cervical opening is still in a relaxed state, premature sexual intercourse can cause retrograde infection, and cervicitis, endometritis, adnexitis, and even pelvic inflammatory disease. The early sex is also likely to cause menstrual blood reflux and endometriosis, so it is more appropriate to have sex 3 days after the end of menstruation.