PARENT SESSION

(W666) VITRIFICATION READY FOR REPRODUCTIVE MEDICINE: BLASTOCYST VITRIFICATION VERSUS CONVENTIONAL CRYOPRESERVATION.

Liebermann, Juergen¹, Knopoff, Elissa¹, Matthews, Jill¹, Erman, Amanda¹, Tucker, Michael^{1, 2}, ¹ Fertility Centers of Illinois, Chicago, IL² Georgia Reproductive Specialists, Atlanta, GA

ABSTRACT- About 14% of all IVF cycles are cycles using frozen embryos for embryo transfer. Clearly, cryopreservation techniques have become an increasingly important therapeutic strategy in assisted reproduction. Vitrification as an alternative to conventional cryopreservation is an ice-crystal-free cooling method for biological materials. Chill-sensitive cells in ART like oocytes and blastocysts have a big advantage in survival rates by avoiding ice-crystallization using vitrification. Objections to cryopreservation aside, vitrification is very simple, potentially faster, cheaper and more consistent than conventional cryopreservation. One year experience with vitrification (VIT) of blastocysts utilizing the Cryotop system of vitrification (Kitazato, Japan), with a mixture of 15% ethylene glycol/DMSO (v/v) + 0.5M sucrose, yielded the following results in comparison with contemporaneous data using the conventional slow cryopreservation (CONV) with 10% glycerol + 0.2M sucrose. All closed Cryotops were secondarily stored inside 5ml liquid nitrogen pre-filled cryovials. The mean age in the VIT group was 34.1 compared to 34.8 in the CONV group. In 61 VIT cycles 139 embryos were thawed, whereas in 137 CONV cycles 317 embryos were thawed. The mean number of embryos transferred was 2.18 in the VIT group and 2.11 in the CONV group. It is clear to date that blastocyst cryosurvival (SURVIVAL) is significantly improved following vitrification: 136/139 (98%) vs. 283/317 (89%) (P=0.005). With increasing numbers of cryopreservation cycles, this is translated into improved overall clinical outcomes: Clinical pregnancy rate (CLIN PR) 54% vs. 47% (P=0.15, NS); Viable pregnancy rate (VIABLE PR) 49% vs. 38% (P=0.10, NS); and Implantation rates (IR) 34% vs. 27% (P=0.055, marginally significant). Even without statistical significant clinical improvement, it is quite evident that after vitrification the cryosurvival is more consistent, allowing greater ease of patient management with transfers (ET) being almost certain to occur. With much shorter procedural protocols, vitrification can be undertaken on a more flexible basis by laboratory staff, and reduces personnel time commitment. Vitrification is now our standard protocol for cryopreservation of all embryonic stages and oocytes within our program.

KEY WORDS: human blastocysts, vitrification, conventional cryopreservation