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

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?

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.

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.

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.