Fluorescence in situ hybridization reanalysis of day-6 human blastocysts diagnosed with aneuploidy on day 3

Human embryo mosaicism: did we drop the ball on chromosomal testing?

“…Fetal/placental mosaicism is one type of potential mosaicism. There are four possible types of embryonic mosaicism: (1) embryos which have an aneuploid ICM and euploid and aneuploid TE cells; (2) embryos which have an aneuploid ICM and euploid TE cells; (3) embryos with a euploid ICM and aneuploid TE cells; and (4) embryos with a euploid ICM and both euploid and aneuploid TE cells [18,19].…”

“…Such results may be due to either decreased mosaicism within TE and ICM cells at the blastocyst stage or to an increased likelihood that the ICM is euploid if the mosaic TE contains some euploid cells [18]. Some fetuses with normal chromosomes have a fully abnormal or mosaic chromosome complement within the placenta [15,16].…”

Preimplantation genetic diagnosis and the biopsy technique: Important considerations

“…In the past, high levels of mosaicism have been reported in cleavage stage embryos [37] and for this reason the analysis of two blastomeres or even more cells with the blastocyst stage biopsy (see the following paragraph) have been introduced. Anyway, data in the literature have shown that embryos with low-moderate chromosome mosaicism on day-3 often self-correct during their development to the blastocyst stage [38][39][40].…”

“…However the following consideration in support of blastocyst culture and biopsy should be taken into account: 1) a low number of embryos to process is more time and cost effective, and 2) most of the embryos that do not reach the blastocyst stage are chromosomally abnormal [52,53]. Blastocyst biopsy seems to be a better strategy as compared to cleavage stage biopsy also because different authors have reported that embryos diagnosed as aneuploid on day-3, later on day-5 have resulted in euploid blastocyst [38][39][40], suggesting the existence of self-correction mechanisms during the transition to blastocyst.…”

Preimplantation genetic diagnosis and screening by array comparative genomic hybridisation: experience of more than 100 cases in a single centre

“…1 Fluorescence in-situ hybridisation (FISH) was first used in PGD for translocation carriers. 2 Due to its technical limitations however, [3][4][5] it has been replaced by array comparative genomic hybridisation (aCGH) in many centres. In our centre, we have previously shown that ORIGINAL ARTICLE rates after preimplantation genetic screening and diagnosis were 45.7% and 41.1%, respectively and the miscarriage rates were 8.3% and 28.6%, respectively.…”