Yutin is an emergency contraceptive pill that is taken orally within 72 hours after having sex without taking measures. The main component is progestin, which can change the thickness of the endometrium and prevent the fertilized egg from being laid. In addition, it can inhibit ovulation, thus achieving the purpose of contraception, which is clinically known as yutin. When taking Yutin, if it is taken in the first half of the menstrual period, it will often cause withdrawal bleeding. If taken in the second half of the menstrual period, the occurrence of withdrawal bleeding will be relatively rare. Therefore, clinically, the effectiveness of contraception is not judged by the presence of withdrawal bleeding, because the time of taking it varies, the situation of withdrawal bleeding also varies.