The contraceptive pill levonorgestrel is an over-the-counter medication for emergency contraception for women, usually taken within three days of unprotected sex between men and women or the failure of other contraceptive methods, and the earlier the pill is taken, the better the results. Levonorgestrel is a short-acting, rapid-acting contraceptive, and its contraceptive mechanism is to inhibit ovulation and fertilization, while increasing the viscosity of the cervical mucus and the resistance to sperm penetration so as to effectively play the role of contraception. The most common adverse reactions are endocrine disorders in women, resulting in dizziness, nausea, fatigue, menstrual cycle disorders, prolonged bleeding, etc. The contraceptive efficiency of this drug is about 95% or more, but there is also a certain chance that it will lead to contraceptive failure.