This data demonstrates an increase in the proportion of genetically normal/balanced embryos at day 5/6 of development. This suggests a strong natural selection process between day 3 and day 5/6 in favour of normal/balanced embryos. These findings support performing PGD testing on day 5/6 of embryo development.

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Chromosomal aneuploidy is responsible for a significant proportion of pregnancy failures, whether conceived naturally or through in vitro fertilization (IVF). In an effort to improve the success rate of IVF, screening embryos for aneuploidy - or pre-implantation genetic screening (PGS) - has been proposed as a means of ensuring only euploid embryos are selected for transfer. Early PGS approaches were based on fluorescence in situ hybridization testing, and have been shown not to improve live birth rates. Recent developments in genetic testing technologies - such as next-generation sequencing and quantitative polymerase chain reaction, coupled with embryo biopsy at the blastocyst stage - have shown promise in improving IVF outcomes, but they remain to be validated in adequately powered, prospective randomized trials. The extent to which IVF with PGS lowers the a priori risk of aneuploidy in ongoing pregnancies so conceived has been poorly described, rendering it difficult to incorporate the potential benefit of PGS into existing prenatal aneuploidy screening regimens such as cell-free DNA testing or conventional combined nuchal translucency and maternal biochemistry assessment. Further data on the sensitivity and specificity of various forms of molecular PGS testing would improve our understanding of the effectiveness and accuracy of these technologies. This, in addition to further research into methods of risk combination and assessment, would allow us to help our patients make better- informed decisions about whether or not to proceed with invasive diagnostic tests.

Purpose Preimplantation genetic testing (PGT) using Karyomapping is used to screen embryos for single gene disorders prior to implantation. While Karyomapping is not designed to screen for abnormalities in chromosome copy number, this testing is based upon a genome-wide analysis of single nucleotide polymorphisms (SNP) and, as such, some chromosome abnormalities are detected. The aim of this study was to validate whether Karyomapping could provide reliable and accurate PGT for a paternal 46,XY,t(10;19)(p15;p13.3) reciprocal translocation. Methods Feasibility/validation for PGT was performed using DNA from the couple, as well as DNA from the paternal parents and from a previous unbalanced pregnancy. Karyomapping was performed using Illumina's HumanKaryomap-12 BeadChip microarray technology. SNP analysis was performed using BlueFuse Multi software (Illumina). Transmission of the translocation was assessed through the analysis of SNP markers on the chromosome regions of interest. Results PGT-SR was determined to be feasible as chromosomal SNP analysis could reliably distinguish normal/balanced outcomes from all unbalanced outcomes. The couple transferred a normal/balanced embryo in an elective single embryo transfer procedure following 2 IVF/PGT-SR cycles. A clinical pregnancy was achieved. Conclusion This is the first report of PGT-SR test validation using Karyomapping for a 46,XY,t(10;19)(p15;p13.3) reciprocal translocation. Karyomapping may offer a means of detecting unbalanced forms of chromosome rearrangements when other PGT platforms fail.

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