Received October 21, 1998
Accepted February 16, 1999

Introduction: To compare an ultrarapid method (URM) modified with dimethyl-sulphoxide (DMSO) to a slow method (SM) with propanediol (PROH) for the cryopreservation of extra human embryos in a program of intracytoplasmic sperm injection (ICSI). Material and Methods: The extra embryos of 170 patients were cryopreserved in a prospective and randomized manner (drawing lots) by a modified URM (Group A) (3M DMSO/0.25 M sucrose/thawing in 3sucrose gradients) or by SM (1.5M propanediol/program O-Cryologic CL-863) (Group B). A total of 80 cycles have been thawed thus far. Results: The mean age ( group A=31.4±4.5; group B=32±4.3) did not differ between the groups (p=0.37). The number of frozen embryos (group A = 6.7±3.2; group B=6.5±3.2) was similar (p=0.76) . Also the number of thawed embryos was similar (p=0.32) for the two groups (group A=7.1±3.1 ; group B=6.6±3.3). Survival rate was superior (p=0.02) for group B (79.8±24.3 % ) than for group A (65.3±29.8%). Cleavage rate was also higher (p=0.0001) for group B (55.4±32.4%) compared with group A (23±21.1%). The number of transferred embryos did not differ (p=0.73) between the groups (group A=3.32±1.33; group B=3.47±1.08). Implantation rate between the groups (group A=6.5%; group B=12.6%) was similar (0.12). Pregnancy rates per thawed and transferred cycles was superior for group B (33.3%; 37.5%, respectively) compared with group A (13.6%; 16.2%, respectively). However, the differences were not significants (p=0.058; 0.34 respectively). Conclusion: The data obtained thus far suggest that the SM is superior to the URM for the cryopreservation of extra embryos after ICSI in terms of survival and cleavage.