Prospective randomized study on the cryopreservation of human embryos with dimethylsulfoxide or 1,2-propanediol protocols.

Objective: To investigate the optimal protocol for cryopreservation of human embryos obtained from IVF.

Design: Prospective randomized study.

Setting: Consenting patients in an academic research environment.

Patients: Couples undergoing IVF.

Interventions: A cohort of 2,220 supernumerary multicellular embryos were obtained from 488 patients who were randomized over slow freezing protocols with dimethylsulfoxide (DMSO, 819 embryos), 1,2-propanediol (699 embryos) or a mixture of DMSO and 1,2-propanediol (702 embryos). A total of 725 embryos have been thawed (DMSO, 232 embryos; 1,2-propanediol, 250 embryos and DMSO and 1,2-propanediol, 243 embryos) for transfer in natural ovarian cycles.

Main Outcome Measures: Embryo survival rate, embryo implantation rate, clinical pregnancy rate (PR), delivery rate, live-birth rate.

Results: The embryo survival rate was significantly higher with the DMSO protocol (52.6%) than with the 1,2-propanediol (32.0%) or the DMSO and 1,2-propanediol protocols (34.9%). The clinical PR per thawing cycle was significantly higher in the DMSO protocol (17.2%) than in the 1,2-propanediol protocol (3.9%). The clinical implantation rate per embryo thawed was significantly different between a DMSO-frozen embryo (4.7%) and a 1,2-propanediol-frozen embryo (1.2%). A DMSO and 1,2-propanediol-frozen embryo had a 3.7% chance of of implantation. The delivery rate per thawing cycle was significantly higher in the DMSO protocol (12.5%) than in the 1,2-propanediol protocol (2.6%). The live-birth rates per embryo thawed were 3.5%, 0.8%, and 2.9% in the DMSO, 1,2-propanediol, and DMSO and 1,2-propanediol groups, respectively.

Conclusion: Supernumerary multicellular embryos as presented in daily clinical IVF practice have the highest chance of survival and of implantation after cryopreservation when DMSO has been used.