RESUMEN
The objective of this study was to evaluate the gestational results obtained with vitrified-thawed human cleavage-stage embryo by two different thaw protocols. Embryo development was observed to cleavage-stage and embryos were cryopreserved by vitrification on day 3 after oocyte retrieval. 51 cycles were thawed using vitrification warming kit with decreasing concentrations of sucrose in 3 dilutions ( 1.0, 0.5 and 0 mol per L respectively) as group 1, 56 cycles were thawed with decreasing concentrations of sucrose in 5 dilutions ( 0.8, 0.6, 0.33, 0.2 and 0 mol per L respectively) as group 2. Embryo survival (> 50 percent intact blastomeres), complete embryo survival (100 percent intact blastomeres), pregnancy and implantation rates were compared, and development rates the day after thawing were also compared. Multivariate analysis showed a significant difference in embryo immediate morphological survival rate, complete survival and clinical pregnancies rate between the two groups respectively (87.0 vs. 98.6 percent, p=0.000; 71.0 vs 82.0 percent embryo subsequent development rates, mean number of transferred embryos was similar between the two groups. (61.4 vs. 61.3 percent, p=0.502; 2.2 +/ 0.5 vs. 2.4 +/- 0.6, p=0.113). In addition, no differences in implantation rate were observed between two groups (17.7 vs. 25.6 percent, P=0.138). No difference in the multiple pregnancy rates was found among the two groups also.