Evolving concepts in the world of vitrification

Cryopreservation by vitrification has become a cornerstone of contemporary assisted reproductive technologies, enabling widespread use of embryo and oocyte banking and fundamentally reshaping IVF workflows. Although recent clinical practice has adopted shortened protocols for both preparation for vitrification and postwarming cryoprotectant elution, the fundamental biophysical principles governing vitrification - membrane transport, cellular dehydration, cooling and warming rates, and ice formation - occur at the same rates, neither faster nor slower, which the present review aims to clarify.

A shortened equilibration phase can achieve intracellular glass-forming conditions comparable, but not identical, to conventional protocols for oocytes. However, certain biological characteristics hinder its application in blastocysts. One-step postwarming rehydration protocols for both blastocysts and oocytes are already being used clinically, but there may exist protocol-specific dependencies on prior cryoprotectant exposure and intracellular solute content.

While emerging data suggest that fast vitrification and warming strategies can yield survival and developmental outcomes equivalent to standard protocols - and may offer logistical and physiological advantages - important knowledge gaps remain. Despite these advancements, there is still a strong need for improved permeability parameter estimation, modelling approaches, and prospective clinical studies to rationally optimize vitrification protocols to ensure robust, reproducible outcomes across diverse patient populations.