Chromosomal abnormalities in embryos

Chromosomal analysis was performed on 1620 embryos generated in vitro by pa tients with a poor prognosis of pregnancy. A diagnosis was yielded in 1596 embryos: 536 (34%) were euploid and 1060 (66%) carried chromosomal abnormal ities. The results revealed a strong association between chromosomal abnorm alities, cellular stage and percentage of fragmentation. In addition, 92% o f embryos with multinucleated cells were diagnosed mosaics, whereas the pre sence of cytoplasmic concentration was associated to 86% chromosomal abnorm alities. The rate of development to expanded blastocysts was dependent on b oth the cleavage stage at the time of blastomere biopsy and the chromosomal status of the embryos. The highest percentage of blastocyst growth derived from embryos with 7-8 cells on the morning of day 3: 68% were generated fr om euploid embryos and 43% from chromosomally abnormal embryos. These findi ngs suggest that morphological criteria alone are not sufficient in poor pr ognosis patients to guarantee the best embryo selection. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.