Objective: To assess if early cleavage embryo is an additional indicator of embryo quality that could be used to increase the effi ciency of IVF and ET. Design: A prospective study. Setting: Centre for Assisted Reproduction, Department of Gynecology and Obstetrics, Medical Faculty, Palacký University, University Hospital, Olomouc. Methods: The study evaluates 62 cycles of conventional IVF in our Centre during 2001 to 2002. All embryos were observed for the presence or absence of ”early cleavage” (EC), i. e. with completed fi rst mitotic division 25 to 26 hours after insemination. The EC embryos were cultivated separately from the so called ”late cleavage” or no early cleavage (NEC) embryos. After the three-day cultivation a maximum of three embryos were transferred in 6-8 cells stage. EC embryos were transferred in 28 cycles, NEC embryos in 18 cycles. The remaining 16 patients with ”combined” transfer of EC + NEC embryos were excluded from the evaluation. The following parameters have been compared: age, number of fertilized oocytes, fertilization rate (FR), number of cryopreserved embryos, number of embryos assessed for EC, number of EC embryos found, number of transferred embryos, pregnancy rate (PR), implantation rate (IR), spontaneous abortions (AB). Statistical analysis was performed by Student’s t-test, χ2 test and Sheffe analysis. Results: EC embryos were found in 71% of conventional IVF (n=44). There were no signifi cant differences in the entry parameters (age, number of fertilized and fertilizing oocytes, number of cryopreserved, assessed and transferred embryos) between the group with EC embryos versus the group with NEC embryos. When EC embryos were transferred, the following parameters were higher: PR (61% vs. 56%), IR (38% vs. 33%), compared to NEC group, while pregnancy loss was lower after EC (4% vs. 11%) compared to NEC. Due to small numbers in the subgroups the results, though suggestive, are not statistically signifi cant (p>0.05). Conclusions: The assessment of early cleavage embryo is one of the criteria for evaluation and selection of suitable embryos prior to transfer which could help in the process of selection to choose the best embryos between embryos of the same morphology on the day of transfer.

        Key words: ”early cleavage” embryos, selection of embryos, quality of embryos, viability of embryos, IVF