Generally emergency contraceptive pills can prevent pregnancy for 1 day and need to be used under medical supervision. Taking emergency contraceptive pills is an emergency remedial contraceptive measure taken after unprotected sex, which needs to be used under the supervision of a doctor and to exclude contraindications such as severe hepatic insufficiency. It is effective within 72 hours after unprotected sex, but the emergency contraceptive pill is only effective for one time, so it can be used for 1 day after taking the pill, and then you need to take other contraceptive measures when you have intercourse again. Side effects such as nausea, vomiting and irregular vaginal bleeding may occur after taking emergency contraceptive pills, which usually do not require treatment and can recover on their own. When the contraceptive efficiency of emergency contraceptive pills is lower than that of regular contraceptive methods, it is necessary to exclude the possibility of pregnancy if menstruation is delayed for more than 1 week after taking the pills.