Comparison of the recovery rate of vitrified hatched blastocysts and the frequency of blebbing between different thawing protocols

This study evaluated the effects of different warming protocols on the recovery rate and blebbing frequency of vitrified hatched blastocysts, aiming to optimize embryo warming methods for improved clinical outcomes. A total of 650 patients (857 cycles) were included, with blastocysts warmed using either the conventional multi-step dilution method or a rapid warming method involving direct immersion in a low-concentration sucrose solution. Recovery rate, blebbing frequency, implantation rate, and clinical pregnancy rate were compared, along with the relationship to embryo morphology at the time of freezing. While recovery rates were similar between the two methods (conventional: 123.67 %, rapid: 124.45 %), the rapid method significantly reduced blebbing frequency (5.1 % vs. 10.9 %, P < 0.05). Implantation and clinical pregnancy rates were similar between the two groups. However, the rapid warming method effectively reduces blebbing while maintaining recovery rates. These findings suggest that rapid warming may improve embryo stability by reducing osmotic stress, supporting its potential clinical benefit and the need for further studies on long-term outcomes such as live birth rates.