[Research on the selection of embryos for transfer using a combined grading for embryo growth rate and morphology and zygote pronuclear morphology].

OBJECTIVE: To evaluate the value of using a combined grading for embryo growth rate and morphology and zygote pronuclear morphology, and to select embryos for transfer in clinical in-vitro fertilization (IVF)/intra-cytoplasmic sperm injection (ICSI). METHODS: In this retrospective study, a total of 2714 normal zygotes (2 pronuclei) from 434 treatment cycles with IVF/ICSI was analyzed between May 2003 and December 2003. These zygotes were divided into two groups (synchronous group and nonsynchronous group) according to the developmental synchrony of pronuclei. The developmental potential of zygotes from these two groups was observed. Embryos for transfer were selected initially by embryo growth rate and morphology, secondarily by zygote grade. The clinical pregnancy rates and implantation rates were compared according to whether the embryos from synchronous group were transferred. RESULTS: There were 2714 normal zygotes, the good-quality embryos (> or = 6 cells, grade I - II) rate of the synchronous group (41.88%, 743/1774) was significantly higher (P < 0.001) than the nonsynchronous group (33.94%, 319/940). Totally 395 cycles transferred at least one embryo from synchronous group, the clinical pregnancy rate was 47.85% (189/395) and implantation rate was 27.49% (273/993). There was no significant difference from 39 cycles which did not transfer embryos from nonsynchronous group. The clinical pregnancy rate was 43.59% (17/39) and implantation rate was 25.00% (21/84). CONCLUSION: The data indicate that there are no significant differences in pregnancy rates and implantation rates between different zygote grade when selecting embryos for transfer by combined grading.