Re-analysis by fluorescence in situ hybridisation of spare embryos cultured until Day 5 after preimplantation genetic diagnosis for a 47, XYY infertile patient demonstrates a high incidence of diploid mosaic embryos: a case report

Mosaicism in 4-8-cell human embryos analysed by fluorescence in situ hybrid isation (FISH) has been widely reported, but few studies have addressed the incidence of mosaicism in more advanced embryonic stages. In the present s tudy we analysed spare human embryos in a case of preimplantation genetic d iagnosis (PGD) for increased risk of aneuploidy because of an infertile 47, XYY man. After replacement of two embryos typed as 1818XX at PGD, six spare embryos (not frozen because of their low quality) were re-analysed on Day 5 for PGD confirmation. Out of five embryos typed as 1818XY at PGD, four we re diploid mosaic (DM) and one was normal in all cells. The sixth embryo, t yped as 18XYY/1818181818X at PGD, was a DM. In spite of the bias of our sma ll series of morphologically low-quality embryos, the surprisingly high pro portion of mosaics (which confirms previous findings) questions the validit y of PGD, but supports the strategy of transferring only the embryos where two blastomeres gave normal and concordant results at PGD. More data are re quired to understand the clinical significance of early diploid mosaicism ( and its impact on implantation rate) and to determine whether some diploid mosaic embryos might be considered safe for transfer. Copyright (C) 2000 Jo hn Wiley & Sons, Ltd.