Comparison Between Slow Freezing and Vitrification in Blastocyst Cryopreservation

s / Placenta 32 (2011) S276–S282 S277 COMPARISON BETWEEN SLOW FREEZING AND VITRIFICATION IN BLASTOCYST CRYOPRESERVATION E. Albani, G. Morreale, P.V. Novara, A. Smeraldi, F. Menduni, P.E. Levi Setti Department of Gynecology, Operative Unit of Gynecology and Reproductive Medicine, IRCCS, Istituto Clinico Humanitas, Rozzano, Milano, Italy Introduction: The introduction of Sentence 151/09 of the Italian Constitutional Court has made it possible to define a custom therapeutic approach based on a patient's clinical history. This Sentence has given us the possibility, with the patient's consent, to inseminate more than 3 oocytes and to transfer an elective number of embryos based on patient age and clinical history. Since we have been allowed to store untransferred supernumerary embryos, we decided to cryopreserve only embryos that were able to reach the blastocyst stage, in order to reduce the number of stored embryos. Blastocyst stage culture was carried out using sequential media and tri-gas incubators. Based on our previous experience with oocyte and cleavage-stage embryo slow freezing, we chose to begin our work using this method. Later, because of improving published results, we decided to switch to a vitrification protocol. This study is a retrospective evaluation of the two procedures after embryo thawing and transfer. Materials and methods: We analysed retrospectively blastocyst thawing performed between May 2009 and December 2010. Two different strategies of blastocyst cryopreservation were compared: slow freezing (group A) and vitrification (group B). Blastocyst morphological survival rate was evaluated 3h after thawing and only vital embryos were transferred. Implantation (IR) and pregnancy rate (PR) were the principal end points of the study. The results were statistically analysed using the t-test and Chi-squared test. Differences were considered significant at p