The failure of the embryos transferred to the uterine cavity to implant is a big blow to the patient and haunts the doctors of the fertility center. Even some infertility patients have repeatedly failed, which, in addition to the cost of money, is also very traumatic to the patient physically and mentally. The reason why the implanted embryos do not successfully implant is always a troubling and highly desired topic. At present, it is believed that it may be related to the following factors: Insufficient endometrial receptivity (1) Abnormal lesions in the uterine cavity, such as congenital malformations of the uterus (bicornuate uterus, longitudinal uterus), endometrial polyps, endometritis and myomas, etc. (2) Thin endometrium: multiple clearings after abortion, irregular menstruation (continuous menstrual flow) or poor blood circulation can cause thin endometrium. (3) Return of fluid in the fallopian tube to the uterine cavity: fluid in the fallopian tube is caused by obstruction of the umbilical (caudal) end of the fallopian tube flowing to the uterine cavity. Persistent fluid accumulation in the uterine cavity may cause embryo implantation failure. (4) Abnormalities in the quantity and quality of adhesion molecules secreted by endometrial cells, etc. Defects in the embryo itself The percentage of chromosomal abnormalities in embryos found in repeat IVF pregnancy failure cases is as high as 60%, so many embryos implanted in the uterus fail to implant because of chromosomal abnormalities in the embryo itself. These chromosomally abnormal embryos sometimes appear to be of normal cell size, divide at a normal rate, and are good grade 1 or 2 embryos on the embryo classification scale. Also, the older the woman is, the greater the chance that the embryo will be abnormal. In addition, the thickening and hardening of the zona pellucida due to the age of the woman and the in vitro culture environment can damage the embryo and cause failure of embryo implantation.