Blastocyst vitrification versus conventional cryopreservation

We compared one year's experience with vitrification of blastocysts using 15%/15% ethylene glycol /DMSO plus 0.5M sucrose, with contemporaneous data using our conventional slow cryopreservation with 10% glycerol plus 0.2M sucrose. It is clear to date that blastocyst cryosurvival is significantly improved following vitrification (97% vs. 90%; p=0.005). With completion of increasing numbers of cryopreservation cycles, this is translating seemingly to improved overall clinical outcomes: clinical pregnancy rate - 52% versus 46%; viable pregnancy rate 51% versus 39%; and implantation rates 36% versus 26%. Even without significant clinical improvement, the evident advantages of vitrification are that cryosurvival is more consistent, allowing greater ease of patient management with transfers being almost certain to occur. Further the need for controlled rate freezing equipment is eliminated. With much shorter procedural protocols, vitrification can be undertaken on a more flexible basis by laboratory staff, reducing personnel time commitment, and may enable more optimal timing of embryo cryopreservation. Vitrification is now our standard protocol for cryopreservation of all embryonic stages and oocytes within our program.