Vitrification versus slow freezing of oocytes: effects on morphologic appearance, meiotic spindle configuration, and DNA damage.

To assess possible effects on subcellular organization after cryopreservation, we compared vitrified and slowly frozen oocytes in terms of their post-warm/thaw morphology, meiotic spindle configuration, and DNA integrity. DNA integrity of cryopreserved oocytes was not altered after the procedures, but vitrification was more effective than slow cooling, as shown by higher survival rate and spindle assessment despite a higher misalignment between meiotic spindle and polar body.