Correlation of D2 and D3 embryo morphology parameters and embryo implantation rate

Objective To investigate the morphological parameters of successfully implanted human embryo and provide evidence for the selection of embryo implantation. Methods A retrospective study of fresh embryo transfers in 113 IVF/ICSI-ET cycles from April 2010 to October 2015 was undertaken in Chinese PLA General Hospital, and according to the implantation rate, the cycles were divided into two groups: 100% implantation group and 0 implantation group. The variables including blastomere number, degree of fragmentation, proportion of mononucleated blastomeres and symmetry of cleavage were observed and the differences of these variables between two groups at day 2 (D2) and day 3 (D3) after being fertilized were compared. Results No significant differences were found between two groups in patients' maternal age, the rate of primary infertility, factor of infertility, basal follicle stimulating hormone (FSH), antral follicle count (AFC), estradiol on hCG day, total dosage of gonadotrophins administration and methods of assisted insemination (P> 0.05). While, the proportion of 4-cell embryos on D2 in 100% implantation group was significantly higher than 0 implantation group (84.82% vs 50.82%, P=0.000), and there was significant difference in proportion of 10% - 25% fragmentation (4.46% vs 12.30%, P=0.032), and the proportion of mononucleated blastomeres and embryos without visible nuclei in all blastomeres between the two groups (17.86% vs 8.20%, P=0.027; 74.11% vs 85.25%, P=0.034). On D3, the proportion of 8-cell embryos in 100% implantation group was significantly higher than 0 implantation group (66.96% vs 45.08%, P=0.001). In contrast, the proportion of ≤7-cell embryos in 100% implantation group was significantly lower than 0 implantation group (15.18% vs 34.43%, P=0.001). But there was no difference in the degree of fragmentation, the proportion of mononucleated blastomeres and symmetry of cleavage on D3 embryos between the two groups. Conclusion Based on the clinical conditions of patients, 4-cell embryo of D2 as well as 8-cell embryo of D3 with less fragments is suggested to be transplanted.