^{Genomics and Molecular Biology}

Embryo aneuploidy screening (PGT-A) using diff erent approaches (FISH, arrayCGH, NGS) has been widely used in IVF setting worldwide. Chromosomal aberrations found in embryos could be as high as 50% from all embryos. Mosaic chromosomal aberrations oft en seen in embryos are well described. Diffi culties in interpreting results are challenging especially when there are no euploid embryos suitable for transfer. Several guidelines are available and they all state that euploid embryo should be preferred over aneuploid or mosaic aneuploid embryo. In case of mosaic embryos, chromosomal aberrations including chromosomes 13, 18, 21, as well as chromosomes which are linked with uniparental disomy, should be excluded. Embryo selfrescue is known mechanism, which in most cases manages to remove cells with aneuploidy and continue development from mosaic aneuploid embryo to child with normal karyotype in up to 80% pregnancies. Th e experience of our clinic has allowed to accumulate knowledge about the mosaic aneuploid embryo PGT-A data interpretation. Data interpretation should be done by specialists – geneticists and molecular geneticists to avoid misdiagnosis and carefully consider possible eff ects of mosaic aneuploidy, especially if there are no euploid embryos for transfer. In practice we have seen several possible outcomes aft er embryo self-rescue – normal and ongoing pregnancy, miscarriage and uniparental disomy..