There are many reasons for the failure of medication abortion, including drug insensitivity, large fetus, poor uterine position other reasons, etc., as follows: 1, drug insensitivity: most of the women are insensitive to the drug mifepristone and misoprostol for medication abortion, so after using medication abortion, especially after taking misoprostol on the third day, the uterus contraction is not obvious, resulting in the pregnancy capsule can not be discharged intact, or 2.Large fetus: If the fetus is larger than 49 days or if the biparietal diameter of the fetus is larger and the gestational sac is larger, these may affect the success rate of medical abortion. 3.Uterine position is not good: If the woman’s uterus has a more pronounced anterior or posterior tilt or if the uterus is in a very bad position, it may also affect the uterine contraction and affect the 4, other reasons: if the process of medical abortion, the woman’s uterus contraction is poor, also easy to lead to the failure of medical abortion, and if the woman has had multiple abortions, or scraping the uterus resulting in scarring of the uterine cavity, the uterine cavity uneven, etc., also easy to lead to failure of medical abortion.