Emergency contraceptive drugs can cause delayed menstruation because they are hormonal drugs that can prolong the endometrial secretion period so that the endometrium does not peel off, change the endocrine hormones in the body, and produce changes in the menstrual cycle, which can cause delayed menstruation, usually for 7-10 days, but as long as it comes normally, there is no big problem. However, if you exclude yourself from the chance of pregnancy when your period is delayed, emergency contraception has a 20% chance of failure, not 100% success, so be sure to exclude yourself from conception. Some women may also experience a small amount of withdrawal bleeding after taking emergency contraceptives, which is also a small amount of endometrial exfoliation, and it takes time to grow, so menstruation will be delayed for a long time.