PGD瓶頸: 假陽性率
PGD切片之TE細胞異常，但ICM細胞正常導致誤以為胚胎染色體異常

J Assist Reprod Genet. 2016 Nov;33(11):1439-1444. Epub 2016 Aug 30.

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

Esfandiari N1, Bunnell ME2, Casper RF3.

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Abstract

There are newly recognized challenges presented by the occurrence of mosaicism in the context of trophectoderm (TE) biopsy for pre-implantation genetic screening (PGS) in in vitro fertilization (IVF) embryos. Chromosomal mosaicism, known to be significantly higher in IVF embryos than in later prenatal samples, may contribute to errors in diagnosis. In particular, PGS may result in discarding embryos diagnosed as aneuploid but in which the inner cell mass may be completely or mainly euploid, thus representing a false positive diagnosis. Although less likely, some embryos diagnosed as euploid could be mosaic and contain some aneuploid cells, possibly impacting their implantation potential. The ability of current diagnostic techniques to detect mosaicism is limited by the number and location of TE cells in the biopsy and by the methodology used for chromosomal assessment. The clinical consequences of mosaicism are dependent on the chromosome(s) involved, the developmental stage at which the mosaicism evolved, and whether TE biopsy accurately reflects the status of the inner cell mass that forms the fetus. Consequently, in patients with no euploid embryos identified on PGS, it may be appropriate to consider the transfer of diagnosed aneuploid embryos if the TE biopsy result is a non-viable chromosomal monosomy or triploidy that could not result in a birth. It should be acknowledged in consent forms that mosaicism has the potential to impact test results and that its detection may be below the resolution of the genetic tests being used. This concept represents a major shift in current IVF practice and ought to be considered given the data, or lack thereof, of the impact of mosaicism on IVF/PGS outcomes.