P24 Validation of preimplantation genetic screening competence and safety as a prelude to preimplantation genetic diagnosis approval in Vietnam

Introduction: Although prenatal diagnosis is widely offered in Vietnam to avoid the birth of a child with a serious genetic disease, preimplantaion genetic diagnosis (PGD) is currently not allowed. To obtain PGD approval, Ministry of Health requires demonstration of competence and safety through well designed research studies. To this end, we designed a prospective study to evaluate survival rate of frozen biopsied embryos and determine post thaw aneuploidy rates. Materials and Methods: A total of 227 day-2-embryos cryopreserved between 2002 and 2007 using either slow freezing or vitrification were consented to research by 37 couples. Following thawing, the embryos were cultured for 24 hours. Only embryos which had further divided and possessed more than 6 blastomeres with less than 20% of fragmentation were selected for the study. One blastomere from each embryo was biopsied using laser assisted hatching system to open its zona pellucida and then the blastomere was fixed in Carnoy’s solution. Chromosomal aneuploidy was assessed by fluorescence in situ hybridization (FISH) analysis using MultiVysion CEP probes (Abbott) for chromomosomes X, Y, 13, 18 and 21. Biopsied embryos were further cultured to the blastocyst stage (72h later). Results: From a total of 227 frozen-thawed embryos, 64.76% (147/227) survived after thawing and 45.81% (104/227) embryos met the selection criteria for further analysis. Of these, 97.1% (101/104) survived after the biopsy procedure and 61.39% (62/101) developed further to blastocyst/hatched embryos. All 101 blastomeres generated clear FISH signals for all 5 chromosomes with 35.6% (36/101) of the embryos demonstrating euploidy. Among 62 blastocyst/hatched embryos that developed, 41.94% (26/62) were euploid and 58.06% (36/62) were aneuploid at the cleavage stage. Conclusion: This study of cryopreserved embryos donated to research conducted at the Infertility Department, TuDu Hospital demonstrates successful biopsy and FISH procedures in a clinical IVF setting. These outcomes compare favorably to that published for well established PGD laboratories by the ESHRE PGD Consortium1 findings demonstrate high competence and safety standards for PGS that should convince the Health Ministry to formulate regulations for clinical PGD and finally approve this reproductive option for at risk couples in Vietnam.