Direct assessment of the rate of chromosomal abnormalities in grade IV human embryos produced by in-vitro fertilization procedure

Abstract

During in-vitro fertilization (IVF) procedures, human preimplantation embryos were classified into four grades according to their morphological appearance under light microscopy. The grade IV group included poor quality embryos. In our IVF programme, these embryos were never transferred or frozen, and were thus available for cytogenetic analysis. Cytogenetic analysis was performed on 411 grade IV embryos from 327 couples participating in the IVF programme. A total of 118 embryos were successfully karyotyped using at least one metaphase. Normal diploid chromosomes were found in only 12 embryos, containing a total of 19 metaphases. All others (90%) showed abnormal or aberrant chromosome complements; 48 were aneuploid and six cases of single chromatids were noted; 14 embryos (11.8%) contained haploid complements, while the remaining 44 exhibited mosaics (2n/3n, n/2n, n/3n) or fragmented chromosome sets. Also, several structural aberrations and rearrangements were observed. These results indicate that the large majority of grade IV human embryos are chromosomally abnormal. This confirms the morphological assessment of the poor quality of these embryos and demonstrates the uselessness of both the transfer and the cryopreservation of grade IV embryos.

Porcine embryo development and fragmentation and their relation to apoptotic markers: a cinematographic and confocal laser scanning microscopic study

“…There are several possible explanations for the negative effects of marked fragmentation on embryonic viability. In human IVF embryos, extensive fragmentation has been associated with a higher incidence of chromosomal abnormalities in less viable embryos (Pellestor et al 1994). Furthermore, according to Antczak & Van Blerkom (1999) fragmentation can result in a depletion of cortically positioned regulatory proteins resulting in a compromising effect on embryo cleavage.…”

Cytoplasmic fragmentation in activated eggs occurs in the cytokinetic phase of the cell cycle, in lieu of normal cytokinesis, and in response to cytoskeletal disorder

“…In human embryos, extensive cytoplasmic fragmentation is almost always accompanied by other cytoplasmic and nuclear anomalies, for instance, blastomere multinucleation and chromosomal mosaicism (Pellestor et al, 1994;Kligman et al, 1996;Laverge et al, 1997;Marquez et al, 2000). Collectively, these abnormalities can explain the abnormal pre-and post-implantation development often seen in fragmented embryos (Jackson et al, 1998;Alikani et al, 1999Alikani et al, , 2000Hardy et al, 2003;Racowsky et al, 2003;Van Royen et al, 2003), though it is important to keep in mind that such embryos are not necessarily non-viable, and that even if non-viable, they may still contain viable cells (Alikani and Willadsen, 2002).…”

Chromosome abnormalities in human embryos

“…Of these, only one-quarter will have all their cells analysed, or <8% overall (Pellestor et al, 1994;Santaló et al, 1995). This means that arrested embryos cannot be analysed at all, and implies that mosaicism is severely underestimated.…”