Vitrification, is an ultra-rapid, manual cooling process that produces glass-like (ice crystal-free) solidification. Water is prevented from forming intercellular and intracellular ice crystals during cooling as a result of oocyte dehydration and the use of highly concentrated cryoprotectant. Though oocytes can be cryopreserved without ice crystal formation through vitrification, it is still not clear whether the process of vitrification causes any negative impact (temperature change/chilling effect, osmotic stress, cryoprotectant toxicity, and/or phase transitions) on oocyte quality, which translates to diminished embryo developmental potential or subsequent clinical outcomes. In this review, we attempt to assess the technique's potential effects and the consequence of these effects on outcomes.

Summary Sentence: The osmolarity changes and water movement during oocyte vitrification and warming procedures are illustrated.

Graphical Abstract