Different probe combinations for assessment of postzygotic chromosomal imbalances in human embryos

Purpose: We compared three different probe combinations for detection of postzygotic mosaic imbalances in human preimplantation embryos. Methods: Two hundred and two spare cleavage stage embryos were hybridized with fluorescently labelled DNA probe mixtures specific to chromosomes X, Y, 18 (N=67), chromosomes 2, 7, 18 (N=71), or chromosomes 13, 16,18, 21, 22 (N=64). Results: An overall higher incidence of abnormalities was detected using probe mixture for five (69%) or three (72%) autosomes compared to one autosome and chromosomes X and Y (54%). The rate of aneuploidy detected increased with the number of amosomes hybridized from 4% (X, Y, 18) to 11% (2, 7, 18) to 19% (13, 16,18, 21, 22). Postzygotic mosaicism comprised the most frequent abnormality detected by all probe combinations, and the percentage detected by each was similar, 48% (X, Y, 18), 56% (2, 7, 18), and 50% (13, 16, 18, 21, 22). Conclusions: A probe combination of five autosomes, particularly those of clinical relevance, may be more beneficial for screening embryos from patients at risk of maternal-age-related aneuploidy. However, all three probe combinations are as efficient at identifying postzygotic mosaicism, and may be used for identifying embryos with less potential of developing to term.