Healthy newborn delivered after very high segmental mosaic embryo transfer- a case report

Mosaicism, the presence of both euploid and aneuploid cell lines within a single embryo, presents a significant challenge in assisted reproduction. While emerging data support the transfer of mosaic embryos in the absence of euploid alternatives, clinical outcomes are variable. Evidence suggests a correlation between the degree of mosaicism and developmental potential, with higher-level mosaicism generally associated with less favorable outcomes, including reduced implantation and higher miscarriage rates. We present the case of an uneventful liveborn delivery resulting from the intentional transfer of an embryo classified via preimplantation genetic testing for aneuploidy (PGT-A), as exhibiting very high-level mosaicism (75%). This transfer was performed due to the absence of any euploid embryos available for selection. This case demonstrates that even embryos with a very high degree of chromosomal mosaicism can result in healthy, ongoing pregnancies and live births. It contributes to the growing body of evidence on the clinical potential of mosaic embryos and highlights the necessity for nuanced, patient-specific counseling when considering such transfers.