Vitrification in sealed containers : Evaluation of a new technique (Rapid-i™) for cleavage stage embryos and blastocysts

Ovarian stimulation in assisted reproduction often leads to the production of a high number of oocytes. After fertilization of these oocytes, the resulting embryos can be cryopreserved for later use. Vitrification is a recently introduced method for cryostoring embryos, showing high survival rates for both cleavage stage embryos and blastocysts. Characteristic of vitrification are high concentrations of cryoprotectants and ultra fast freezing which makes the material glassily. A major concern with vitrification has been the direct contact of the cryo-solutions with liquid nitrogen. Therefore, sealed containers have been developed and one of these is the Rapid-i™ made by Vitrolife Sweden AB. We evaluated this new device using embryos not suitable for embryo transfer or cryopreservation for clinical purposes. Embryos at cleavage stages were first vitrified and then warmed. Outcome parameters were cryosurvival and development to the blastocyst stage. Blastocysts were randomised between the established VitroLOOP™ and the Rapid-i™ as carriers. Outcome parameters were cryosurvival and further development. Our results show that Rapid-i™ gives good survival rates in vitrification for cleavage stage embryos and blastocysts