Effect of morphological characteristics of D2 embryo on the ability of in vitro development and implantation potential of embryos

Objective:To explore the effects of all kinds of morphological characteristics of D2 embryo on the quality of D3 embryo,development of D6 blastocyst and implantation potential of embryos,in order to evaluate the clinical application value of morphology of D2 embryo in in vitro fertilization-embryo transfer(IVF-ET). Methods:The morphological characteristics of D2 embryo were observed at 42~44 hours after conventional IVF or intracytoplasmic sperm injection(ICSI).The embryos were divided into different groups according to the cell number of D2 embryo,the proportion of particles,the degrees of size and uniformity of blastomere and the nuclear characteristics in blastomere;the rates of good quality D3 embryos,the blastulation rates of D6 blastocyst and implantation rates were compared among different groups.The embryos were divided into grade A(a single nucleus could be found in every blastomere),grade B(at least one blastomere had no nucleus),grade C(no nucleus was found in every blastomere) and grade D(at least one blastomere had multiple nuclei(≥2 nuclei)) according to the nuclear characteristics in blastomere. Results:The ability of in vitro development and implantation potential of tetraploid embryos were superior to those of the other two groups,the rate of good quality D3 embryos and implantation rate of tetraploid embryos were higher than those of tetraploid embryos.The ability of in vitro development and implantation potential of D2 embryos(the proportion of particles≤10%) were superior to those of embryos(the proportion of particles10%).Compared with the other groups,the embryos in group A had the highest ability of in vitro development and implantation potential,as well as the D2 embryos with high quality morphology.In group D,the rate of good quality D3 embryos was significantly lower than those in the other groups,and among the 27 transplanted embryos in group D,no embryo implanted. Conclusion:The tetraploid embryos(the proportion of particles≤10%) have relatively high ability of in vitro development and implantation potential;at the same time,nuclear evaluation of D2 embryos can predict the embryonic developmental ability in vitro and in vivo independently,the embryos with every blastomere having single nucleus should be considered preferentially;the existence of multiple nuclei in blastomere is a manifestation of impaired developmental potential.