Journal Article

Chromosomal mosaicism throughout human preimplantation development <i>in vitro</i>: incidence, type, and relevance to embryo outcome

Magdalena Bielanska, Seang Lin Tan and Asangla Ao

in Human Reproduction

Published on behalf of European Society of Human Reproduction and Embryology

Volume 17, issue 2, pages 413-419
Published in print February 2002 | ISSN: 0268-1161
Published online February 2002 | e-ISSN: 1460-2350 | DOI:
Chromosomal mosaicism throughout human preimplantation development in vitro: incidence, type, and relevance to embryo outcome

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BACKGROUND: A large percentage of in-vitro generated cleavage stage human embryos are chromosomally mosaic, consisting of both normal (diploid) and abnormal (non-diploid) cells. The present study characterized mosaicism at each stage of cleavage division and examined its effect on preimplantation development in vitro. METHODS: A total of 216 normally fertilized (two-pronucleate) embryos which were not selected for transfer to the patients were analysed for chromosomal abnormalities using multi-colour fluorescence in-situ hybridization DNA probes specific for three to five of nine different chromosomes (X, Y, 2, 7, 13, 16, 18, 21, 22). RESULTS: Overall, 48.1% of embryos were mosaic. The frequency of mosaic embryos increased from 15.2 to 49.4 to 58.1%, from the 2–4-cell to 5–8-cell to morula stages respectively, and the types of non-diploid cells detected were mostly aneuploid or chaotic. The incidence of mosaicism at the blastocyst stage was 90.9%; however, most of the mosaicism comprised diploid and polyploid cells. Arrested mosaic embryos had a higher incidence of chaotic abnormalities, and higher proportions of abnormal cells compared with the non-arrested group. CONCLUSIONS: Post-zygotic errors leading to mosaicism may occur, and persist throughout preimplantation development in vitro. Our results suggest that mosaicism involving multiple chromosomal imbalances and/or imbalances affecting a high proportion of cells in an embryo appear to impair development to the blastocyst stage.

Keywords: chromosomes; embryo mosaicism; fluorescence in-situ hybridization; preimplantation development

Journal Article.  6167 words. 

Subjects: Reproductive Medicine

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