Re-analysis of 166 embryos not transferred after PGS with advanced reproductive maternal age as indication

BACKGROUND: In a randomized controlled study aiming to test the effectiveness of preimplantation genetic screening (PGS) in women of advanced maternal age, embryos diagnosed as chromosomally abnormal and those with no diagnosis were fixed for reanalysis. The aim of this study was to determine how well the chromosomal constitution of one biopsied blastomere reflects the status of the entire embryo. METHODS: One hundred and seventy-three embryos diagnosed as chromosomally abnormal, 22 with no PGS result and four degenerated embryos originally diagnosed as normal were fixed and reanalysed by fluorescence in situ hybridization. RESULTS: In total, 199 embryos were fixed, of which 166 were successfully reanalysed. One hundred and sixty embryos were found to be chromosomally abnormal; 48 of the reanalysed embryos with an initial diagnosis (149) had at least one cell with exactly the same chromosomal constitution shown in the first PGS analysis (34.2%). The reanalysis confirmed the initial overall chromosomally abnormal status of the embryo in 95.9% of the cases. Of all chromosomally abnormal embryos, 4.1% were diagnosed as false positive. The risk for false negative rate was at least 4.1%. CONCLUSIONS: PGS seems to be a good method for selecting against chromosomally abnormal embryos but not for determining an embryo's exact chromosomal constitution.