Levonorgestrel is an emergency contraceptive, the main ingredient of this contraceptive is a highly effective progestin, this drug will cause the cervical mucus to increase the viscosity of the cervical mucus, so that the sperm is not easy to pass through, and to inhibit ovulation, affecting the implantation of fertilized eggs, so as to play a role in contraception. However, this drug also has a lot of side effects, changing the normal secretion of the gonads, so it will cause endocrine disorders and menstrual disorders. This drug can not be applied as a regular contraceptive, not more than three times a year, not more than twice a month, if you take too much, it will cause irregular vaginal bleeding or infertility.