Media temperature control: A potentially important  quality control parameter in human oocyte vitrification

Purpose: The purpose of this study is to evaluate the role of controlling media temperature during human oocyte vitrification. This study aimed to retrospectively compare embryological outcomes following oocyte warming, fertilisation and embryo development to the blastocyst stage for two separate periods during which the vitrification solution temperature was not controlled and controlled. Method: A retrospective observational study was conducted at Ventus IVF Center, Cyprus (March 2024–February 2025), evaluating the effect of vitrification solution temperature during vitrification on oocyte survival and embryological outcomes. All oocytes were sourced from 16 donor cycles, with informed consent obtained. Oocytes were vitrified either under uncontrolled ambient conditions (n = 87 oocytes) or with temperature control (n = 83 oocytes) implemented using a heated stage. Vitrification and equilibration solution temperatures were recorded using a calibrated UNI-T UT322 thermometer. Results: There were no significant differences in baseline characteristics of oocyte donors between the controlled and uncontrolled temperature groups (p > 0.05). During vitrification, vitrification media temperature was significantly higher in the controlled group (23.85 ± 0.43°C) compared to the uncontrolled group (19.65 ± 0.43°C; p < 0.001). No significant differences were observed in oocyte survival post-warming (82/83 vs. 80/87; p = 0.081) or fertilisation rates (69/82 vs. 70/87; p = 0.671) between groups. Compared to the controlled group, the uncontrolled group showed markedly higher developmental arrest at the pronuclear (10/70 vs. 0/69), post-pronuclear (20/70 vs. 0/69), and cleavage (35/70 vs. 0/69) stages, and significantly reduced blastocyst formation (5/70 vs. 56/69; all p < 0.001). Conclusion: Maintaining vitrification solution temperature rather than relying on ambient conditions, significantly improves oocyte vitrification efficiency and pre-implantation embryo development parameters.