The medication to prevent pregnancy is the emergency contraceptive pill, the most commonly used contraceptive pills are levonorgestrel, mifepristone, both drugs can prevent pregnancy after sex without contraception, however, within 72 hours of oral is effective, if more than 72 hours to take it will not work. The success rate of emergency contraceptive pills is only 90%, so there are still about 10% of people who take emergency contraceptive pills will also get pregnant normally. Therefore, if you do not want to have children, you must do a good job of effective contraceptive measures, such as oral short-acting contraceptive pills or placement of contraceptive rings, which are more reliable methods. Emergency contraceptive pills should not be applied as regular contraceptive measures, and taking too many of them will cause endocrine disruption.