Vitrification, an efficient cryopreservation procedure but still rising some debates

Abstract

SummarySince the implementation of efficient vitrification techniques, the percentage of cryopreservation cycles worldwide increased dramatically. Moreover, there is a trend toward "vitrification-all strategy" after IVF with single blastocyst transfer in a subsequent warmed cycle. With the final objective of increasing the cumulative pregnancy rate, efficient, standardized, reliable, harmless, aseptic vitrification is mandatory. Vitrification procedure consists of several steps. Some of them generate debates. In this review several phases of the procedure that aroused debates are discussed. For example: (1) which blastocysts to select before and after vitrification? (2) is it required to collapse the blastocoele? (3) is scepticisms about the use of high concentrations of cryoprotectants justified? (4) is it possible to vitrify in reduce cooling conditions and achieve aseptic vitrification? (5) is the warming process more important than the cooling one, (6) and finally concerns about the stability of vitrified biological materials over time.