Simplified vitrification-warming protocol in donor oocytes: artificial intelligence-based oocyte competence and clinical outcomes.

RESEARCH QUESTION: Is the simplified procedure for vitrification and warming as efficient as the conventional protocol for human donor oocytes in terms of laboratory and clinical outcomes?

DESIGN

This prospective, randomized, proof-of-concept study used sibling donor oocytes. Mature oocytes from 20 donor cycles (n = 245) were randomized at the Cryotop level to a simplified or conventional protocol. In the simplified protocol, oocytes were exposed to equilibration and vitrification solutions for 1 min each before immersion in liquid nitrogen. At warming, cryoprotectant dilution was performed in a single 1 min step using thawing solution at 37°C. The conventional protocol used standard 12-15 min stepwise equilibration, 1 min vitrification, and 10 min multistep warming. Laboratory outcomes, clinical outcomes after single-embryo transfer, and artificial intelligence (AI)-based assessment of oocyte competence before vitrification and after warming were evaluated.

RESULTS

Oocyte survival was comparable between the simplified and conventional protocols (97.7% versus 97.4%, respectively). No statistically significant differences were observed in fertilization (83.5% versus 77.7%), usable blastocyst (41.5% versus 47.1%), or good-quality blastocyst (32.1% versus 41.4%) rates. A total of 17 blastocysts were transferred, resulting in comparable implantation (80.0% versus 71.4%) and ongoing pregnancy (60.0% versus 57.1%) rates. AI-based assessment showed comparable estimated oocyte competence before vitrification and after warming, with similar proportions of cohorts classified as having >95% versus ≤95% probability of obtaining at least one blastocyst.

CONCLUSIONS

The use of a single-step approach during equilibration and dilution of cryoprotectants - the simplified procedure - yields clinical and laboratory outcomes comparable to conventional vitrification and warming protocols.