Emergency contraceptive pills are to be taken once after a single sexual intercourse, usually within 72 hours, and can have a contraceptive effect. Emergency contraceptive pills contain more hormones, will affect the body’s normal hormone secretion, inhibit ovulation, but also make the cervical mucus thicker, not conducive to the passage of sperm. In addition, emergency contraceptive pills also inhibit the role of fertilized egg implantation, generally need to be taken within 72 hours after sex once. Generally, a single emergency contraceptive pill can only manage one time of sexual intercourse. Emergency contraceptive pills may produce dizziness, fatigue and other adverse reactions when used, for serious liver and kidney function abnormalities, people with thrombotic diseases can not be used. Use should pay attention to under the guidance of the doctor, avoid unauthorized use of the drug. If there is no intention to prepare for pregnancy and have unprotected sex, it is recommended to consult a doctor in time, under the guidance of the doctor to carry out standardized treatment to prevent pregnancy.