Embryonic factors: Chromosomes are carriers of genetic material and are crucial in determining the development of the embryo. A good quality embryo is one that has good morphology, a number of cells that matches the developmental time, and few fragments, but such embryos can also have chromosomal abnormalities that can lead to embryo implantation failure, so even the transfer of a good quality embryo is not guaranteed to be 100% successful. Maternal factors: Successful embryo implantation requires not only embryos with developmental potential, but also a healthy environment for implantation, so if the mother has the following problems, the embryo will also fail to implant Poor uterine environment: When there are various uterine abnormalities such as polyps, submucosal fibroids, uterine adhesions, endometritis or thin endometrium, the chances of successful implantation may be reduced. Fluid in the fallopian tubes: Fluid in the fallopian tubes contains various inflammatory mixtures that can damage the newly transferred embryos, thus greatly reducing the chances of embryo implantation. Immune factors: If the maternal immune mechanism is abnormal, pregnancy will result in rejection of the embryo by the endometrium and abnormally elevated activity of systemic or local natural killer cells, which can have a toxic effect on the embryo and prevent implantation. Coagulation abnormalities: Embryo implantation depends on having blood supply from the endometrium. Inadequate blood supply to the endometrium and thrombosis in the small blood vessels of the placenta can cause decreased chance of embryo implantation or increased risk of miscarriage. Psychological factors: Bad mental and psychological factors such as anxiety, stress and depression may lead to endocrine disorders, which may also activate the body’s stress system and cause disorders in the contraction of uterine muscles. Therefore, the reasons for failure of quality embryo implantation after transfer are very complex and highly individual, each person’s body condition is different, so it is necessary to analyze the specific situation and find the appropriate treatment countermeasures to improve the embryo implantation rate.