Previously reported and here added cases demonstrate euploid pregnancies followed by PGT-A as mosaic as well as aneuploid designated embryos

BackgroundAfter the longest time opposing all transfers of embryos by preimplantation genetic testing for aneuploidy (PGT-A) diagnosed as chromosomal-abnormal, the field has over recent years slowly been moving toward selective transfers of by PGT-A as mosaic diagnosed embryos, but is still rejecting transfers of embryos by PGT-A defined as aneuploid.MethodsUpon review of the literature, we report published cases of euploid pregnancies following transfers of PGT-A as aneuploid diagnosed embryos and add several additional, ongoing cases at our center.ResultsAmong the published cases from our center, we identified seven euploid pregnancies from aneuploid embryos, four of which preceded the PGT-A industry's 2016 switch from binary euploid - aneuploid reporting to euploid, mosaic, and aneuploid reporting. That those four cases post 2016 PGT-A definition involving mosaic embryos, therefore, cannot be ruled out. Since then, we recently established three additional ongoing pregnancies from transfers of aneuploid embryos which still await confirmation of euploidy after delivery. A recent fourth pregnancy from the transfer of a trisomy 9 embryo miscarried before a fetal heart. Outside our own center's experience, the literature revealed only one additional such transfer, involving PGT-A as a chaotic-aneuploid diagnosed embryo with six abnormalities, leading to normal euploid delivery. In reviewing the literature, we furthermore demonstrate why current PGT-A reporting that differentiates between mosaic and aneuploid embryos based on relative percentages of euploid and aneuploid DNA in a single trophectoderm biopsy of on average 5-6 cells, is biologically non-sensical.ConclusionBasic biological evidence and a clinically still very limited experience with transfers of PGT-A as aneuploid labeled embryos demonstrate beyond reasonable doubt that at least some aneuploid embryos can lead to healthy euploid births. Therefore, this observation establishes beyond reasonable doubt that the rejection of all aneuploid embryos from transfer reduces pregnancy and live birth chances for IVF patients. Whether (and to what possible degree) pregnancy and live birth chances differ between mosaic and aneuploid embryos, remains to be determined. The answer will likely depend on the aneuploidy(ies) of an embryo and to what degree percentages of mosaicism in a single, on average 5/6-cell trophectoderm biopsy can reflect the ploidy-status of a complete embryo.

Automated summary

Despite the previous strong opposition, the field has gradually shifted towards selective transfers of embryos diagnosed as mosaics through PGT-A, while rejecting transfers of embryos defined as aneuploid. Published cases and ongoing cases demonstrate that aneuploid embryos can still result in healthy euploid births.