Purpose
The objective of this study was to compare the effects of two warming protocols (three step vs. one-step) on re-expansion and post-warming survival of human blastocysts previously vitrified using the standard vitrification protocol.
Methods
One hundred vitrified blastocysts were included in the study; 50 blastocysts were warmed using the standard warming protocol, and 50 were warmed using the diluted one-step warming protocol (DS 37 °C, 3 min; WS RT 5 min; culture dish until embryo transfer).
Results
There was no significant difference in survival 2 h post-warming between the standard warming protocol and the diluted one-step warming protocol (98% vs 94%; p = 0.3), nor was there any difference in the number of embryos that were completely re-expanded, hatching or hatched when evaluated 2 h post-warming (84% vs 80%; p = 0.6). Those results indicate that vitrified blastocysts were able to survive equally between the two investigated protocols.
Conclusion
The diluted one-step warming of vitrified blastocysts in 0.5 M sucrose showed no negative effects on embryo re-expansion and post-warming embryo survival when compared with the standard warming method. Therefore, the elimination of the first step of the standard warming procedure (TS, 37 °C, 1 min), the most difficult at a practical level, not only allows the reduction of the execution time, but above all, reduces the learning curve while maintaining effectiveness.
