Table 2.

Methods of oocyte viability assessment. Several invasive assessment methods exist that may be used to further improve experimental cryopreservation and thawing protocols. However, especially useful are methods that permit non-invasive assessment of oocyte viability following warming/thawing to better aid in selection of high quality oocytes and resulting embryos for subsequent clinical use

Target	Assessment	Reference
Pyruvate uptake	Decreased pyruvate uptake can be used as a proxy for cryo-induced stress on the oocyte. If analytic methods are sensitive enough and turn-around times appropriate, cells could be cultured individually to aid in selection of embryos for transfer that came from higher quality oocytes.	[52]
LDH appearance	Lactate dehydrogenase (LDH) appearance in the media surrounding the oocyte can be used to indirectly assess cryo-induced membrane damage.	[13]
Meiotic spindle stability/formation	Polscope imaging allows rapid visualization of the meiotic spindle of living and unfixed MII oocyte without compromising viability. Those oocytes displaying an intact meiotic spindle may be more suitable for use.	[50, 95]