Vitrification of human early cavitating and deflated expanded blastocysts: clinical outcome of 474 cycles

Abstract

Purpose The present study was undertaken to evaluate and compare the post thaw survival, implantation and pregnancy rates of vitrified human early cavitating blastocysts with deflated expanded blastocysts. Material and methods Supernumerary blastocysts were vitrified in 30% ethylene glycol-dimethyl sulphoxide based solution using cryoloop. Fully expanded blastocysts were deflated by gentle aspiration of the blastocoelic fluid using a micromanipulator until the cavity collapses prior to vitrification. Results Of the 576 vitrified blastocysts, 545 (94.61%) survived thawing in the early cavitating blastocyst group which was significantly higher than deflated expanded blastocyst group, in which only 370 survived thawing out of 459 (80.62%). However, no significant difference was observed in implantation and pregnancy rates between early cavitating and deflated expanded blastocyst groups. Conclusions Early cavitating blastocyst would be the ideal stage for cryopreservation of human blastocysts as it has higher survival rate and avoids additional invasive procedures like deflation of the blastocoele.

Cryopreservation of mammalian embryos: Advancement of putting life on hold

“…An even higher post-thawing survival rate could be obtained by artificially collapsing blastocoels before vitrifying (Hiraoka et al, 2004). The consistently high postthawing survival rate and the similarity between vitrified embryos and nonvitrified embryos, in terms of their respective implantation rates and pregnancy rates, have been reported repeatedly (Mukaida et al, 2003;Hiraoka et al, 2004;Huang et al, 2005;Isachenko et al, 2007;Kartberg et al, 2008;Raju et al, 2009;Wennerholm et al, 2009).…”

Transfer of blastocysts derived from frozen-thawed cleavage stage embryos improved ongoing pregnancy

“…Blastocysts are usually considered as pre-implantation embryos which have passed the genomic activation step and have a greater developmental potential [1].…”

Slow freezing and vitrification of mouse morula and early blastocysts

“…This is supported by human morula and early blastocysts having improved survival rates compared to fully expanded blastocysts after vitrification, however, when the cavity of expanded blastocysts underwent artificial shrinkage, survival rates were equivocal [9]. A further study demonstrated vitrification of early blastocysts resulted in improved survival compared to artificially collapsed expanded blastocysts while implantation and pregnancy rates were the same [30]. Overall the conclusion from these studies is that the morula/early blastocyst may be the best stage for cryopreservation as the embryo is better equipped to counteract osmotic changes, while the lack of the large fluid filled cavity circumvents the need to extended periods of exposure to cryoprotectants or artificial cavity collapse.…”