The project belongs to the field of reproductive medicine. In recent years, due to the adoption of a sequential culture system for embryo cultivation, it has become relatively easy to cultivate blastocysts, and culturing blastocysts is more conducive to selecting embryos with greater vitality. Blastocyst transfer can not only reduce the number of embryos transferred but also significantly improve implantation rates and pregnancy rates, as well as decrease the incidence of multiple births. However, using traditional cryopreservation techniques to preserve remaining blastocysts after transplantation inevitably leads to cryoinjury, making the survival rate of blastocysts after program freezing and the pregnancy rate very unstable. The vitrification technique for preserving blastocysts solves this problem. Director Tong Guoqing has successively served as a professor at Nanjing Medical University, a doctoral supervisor, director of the Reproductive Medicine Center at Nanjing Maternal and Child Health Hospital, director of the Reproductive Medicine Center at Shanghai First Affiliated Hospital of Fudan University, and chief of the Reproductive Medicine Department at Shanghai Shuguang Hospital affiliated with Shanghai University of Traditional Chinese Medicine. During this period, he actively carried out work and applied it to clinical practice. Achieved good clinical results: 1. First discovered that vitrified frozen blastocyst transfer has a higher pregnancy rate than fresh blastocyst transfer. First discovered that ovulation induction drugs have an adverse effect on the endometrium of Chinese women, leading to a decrease in the pregnancy rate after fresh blastocyst transfer. Scientific papers were published in international journals such as Fertility and Sterility, Journal of Ovarian Research, etc. As a very valuable scientific discovery, it received reprints and promotion from the international media Reuters. 2. First established and applied the vitrification method to preserve surplus IVF embryos in humans, and first discovered in a mouse model study that the survival rate and developmental potential of 8-cell stage and morula stage embryos after vitrification and thawing are higher than those of 2-4 cell stage embryos. This was applied bidirectionally in clinical practice. Improved efficiency in the transfer of frozen embryos during human IVF treatment. Scientific findings published in international journals such as RBM Online, Journal of Reproduction and Genetics, Zygote.