After taking emergency contraceptive pills, some women’s menstruation may be normal, while others may experience early or delayed menstruation or withdrawal bleeding. Commonly used emergency contraceptives include levonorgestrel, mifepristone, etc. Their mechanism of action is to significantly inhibit ovulation, thin the uterine lining, prevent the pregnancy egg from implanting, and increase cervical viscosity and sperm penetration resistance. Emergency contraceptive pills usually affect hormone levels in the body, which may lead to early or delayed menstrual cycle in the month, or vaginal bleeding within a week after stopping the pill, which is normal. However, if menstruation is delayed for more than a week, pregnancy is possible, and if irregular uterine bleeding or severe lower abdominal pain occurs three to five weeks after taking the pill, ectopic pregnancy may occur. When patients take emergency contraception, irregular vaginal bleeding and severe pain in the lower abdomen, they should promptly go to the hospital and take effective treatment under the guidance of the doctor. It is generally recommended that women should choose safer contraception with fewer side effects, such as condoms or can wear a ring to prevent pregnancy, and then take emergency contraceptive pills as a last resort.