Emergency contraceptive pills are effective when taken within 72 hours of intercourse. Because the emergency contraceptive pill belongs to estrogen, progesterone drugs, the main purpose is to affect ovarian ovulation, because the formation of a fertilized egg needs to be combined with sperm and egg, emergency contraceptive drugs contraceptive principle is to prevent the formation of fertilized eggs as far as possible, so as to play the effect of contraception. Emergency contraceptive pills are often taken after ejaculation in the body, the sooner the better, clinical advice is not more than 72 hours at the latest; it is recommended to do a good job before sexual intercourse appropriate contraceptive measures, such as wearing a condom, etc., to minimize the number of times a woman takes emergency contraceptive pills, because emergency contraceptive pills for women is a certain amount of harm. If any adverse reaction occurs after taking emergency contraceptive drugs should immediately go to the hospital for examination, actively cooperate with the doctor’s treatment, and under the guidance of the doctor to carry out the corresponding treatment, do not use drugs indiscriminately, so as not to miss the opportunity of the disease.