Pregnancy after taking the emergency contraceptive pill, mainly consider the following three reasons: first, the patient is not sensitive to the drug, the contraceptive rate of the emergency contraceptive pill itself is only about 80%, if the patient is not sensitive to the drug, it may further reduce the role of the contraceptive pill. Second, to consider the drug absorption is not good, if the patient itself has gastrointestinal diseases, the patient’s absorption of the drug may decline; or the patient consumes food or drinks too early after taking the emergency contraceptive pill, this situation may reduce the effect of the emergency contraceptive pill. In general, it is recommended that patients take the emergency contraceptive pill within two hours before and after the best fasting, which is conducive to the absorption of drugs. Third, to consider the concentration of the drug is not enough, because the emergency contraceptive pill are finished products, there is no way to adjust the dosage according to the weight of the patient, if the patient weighs too much, the concentration of this drug may be relatively insufficient, so it will lead to failure after taking the emergency contraceptive pill.