Does additional hybridization also improve preimplantation genetic screening results?

Mir et al. have evaluated the impact of additional hybridization rounds on FISH accuracy in preimplantation genetic screening (PGS) of aneuploidy. In a retrospective analysis of 1000 PGS cycles, embryo biopsy was performed on day 3. A greater number of embryos were diagnosed as chromosomally normal and were available for transfer after discarding 'false monosomies' and decreasing the number of noninformative embryos. The error rate for the FISH technique was 17.3% without and 5% with additional probes. A randomized controlled trial is needed to demonstrate improved clinical outcome. However, major obstacles in cleavage-stage PGS are chromosomal mosaicism and incomplete analysis. Therefore, polar body and/or trophectoderm analysis using 24 chromosome microarrays might be better alternatives.