It is normal to have no reaction after taking emergency contraceptive drugs, and some of them may have no symptoms. The main adverse reactions to emergency contraception are gastrointestinal reactions, irregular vaginal bleeding or menstrual disorders, most of which can be relieved on their own, but a very small number of cases with heavy bleeding or severe gastrointestinal reactions need to be treated with medication. Emergency contraception is a remedial method used by women to prevent unwanted pregnancy after unprotected sex or within a few hours or days after the failure of contraception. The main methods are the insertion of an intrauterine device (IUD) within five days or the administration of a combination of estrogen and progestin within 72 hours, but it is necessary to take the right amount to avoid contraceptive failure.