Effect of different rehydration temperatures on the survival of human vitrified-warmed oocytes

To evaluate the effect of different exposure temperatures during the dilution process on the survival rate of vitrified oocytes and following development.

Patients were divided at random into two groups for different dilution temperature (20-22 °C, RT group; 37 °C,37 °C group) according to computer-generated random numbers on the day of oocyte warming. The survival and fertilization rates of vitrified oocytes as well as the implantation and clinical pregnancy rates of the resulting embryos were recorded.

A total of 662 and 676 oocytes were warmed in the 37 °C group and RT group, respectively, and significant difference was observed in the survival rate between 37 °C group (88.37%) and RT group (79.88%) (P = 0.0000). There was significant difference between the survival rate of 37 °C group (87.27%) and RT group (75.64%) in nondonor patients (P = 0.0001). Multiple linear regression analysis showed that dilution temperature (β = 0.079, P = 0.017) and clinical outcomes of fresh cycles (β = 0.063, P = 0.001) were significantly and independently associated with survival rate. No significant difference was found between the 37 °C group and RT group in: fertilization rate (66.67 versus 65.37%), implantation rate (20.0 versus 19.46%), clinical pregnancy rate (37.5 versus 35.0%).

In conclusion, the results of this study give supportive evidence of the application of 37 °C in the dilution process, especially for oocytes of poor quality. Further studies with well-controlled experimental groups are needed to optimize protocols for human oocyte vitrification.