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.