Neonatal and clinical outcomes after the transfer of embryo recognized as mosaic after preimplantation genetic testing for aneuploidy (PGT-A)

Research question Comparing the clinical and neonatal outcomes of mosaic embryo transfers (MET) and euploid embryo transfers (EET). Design: A retrospective cohort study where the Implantation Rate (IR), Life Birth Rate (LBR), and spontaneous miscarriage rates were compared between 513 euploid embryos (EE) and 118 mosaic embryos (72 whole chromosomes mosaic (WCM), 40 segmental mosaic (SM) and six complex mosaic). Blastocysts were analyzed using PGT-A with Next-generation sequencing (NGS), followed by a single thawed embryo transfer. Trophectoderm (TE) biopsies were classified as mosaic if they had 20%–80% abnormal cells. Results: Overall, EET resulted in significantly higher IR (47.0%) and LBR (40.7%) compared to MET (IR-39.0%, LBR-28.8%) and WCM embryos (IR-37.5%, LBR-22.2%). SM embryos had both an IR (47.5%) and LBR (45.0%) comparable to EE. Mosaic embryos with a high percentage of aneuploidy cells (≥60%) showed a significantly lower LBR (10.5% vs. 40.7%) and a high spontaneous miscarriage rate (60.0% vs. 12.0%), compared to EE. Neonatal outcomes did not differ significantly between the mosaic and euploid groups. While women who had MET were recommended to have prenatal genetic testing, only a minority did so; nevertheless, the results are reassuring in that none of the tests performed demonstrated any abnormalities. Conclusions: Compared to EE, mosaic embryos were associated with a lower LBR, and mosaic embryos with high aneuploidy percentage (≥60%) should have low transfer priority. Embryos that were SM have similar clinical outcomes compared to EE. Finally, the neonatal outcomes did not differ significantly between euploid and mosaic groups