Why do array-CGH (ACGH) euploid embryos miscarry? Reanalysis by NGS reveals undetected abnormalities which would have prevented 56% of the miscarriages

Abstract

The objective of this study was twofold; first we wanted to determine the number of blastocysts needed at a certain age to produce at least one euploid blastocyst (>95%) through PGS using whole comprehensive chromosome screening. Secondly, we evaluated the chance of obtaining a euploid embryo in the next cycle after obtaining all aneuploid embryos. DESIGN: Retrospective cohort study. MATERIALS AND METHODS: 10,852 cycles of PGS were performed using blastocyst biopsy and analyzed by array Comparative Genomic Hybridization (aCGH). A total of 58,798 embryos were analyzed. IVF cycles were performed at multiple fertility centers and biopsies sent to a reference laboratory for analysis. Some poor prognosis patients accumulated embryos from several cycles and then performed PGS (''embryo banking''). RESULTS: There was no correlation between cohort size of blastocyst analyzed and euploidy rates, but there were significant differences between euploidy rates and maternal age (p< 0.001). Euploidy rates 65%, 56%, 46%, 33%, 19% and 13% for egg donors were observed for ages 42 years old, respectively.The cumulative number of blastocyst needed to produce at least one euploid blastocyst with 95% or higher chance was calculated from single cycles or embryo banking cycles from the same patient and is shown in the below table.

Detailed investigation into the cytogenetic constitution and pregnancy outcome of replacing mosaic blastocysts detected with the use of high-resolution next-generation sequencing

“…In another study, reanalysis by means of hr-NGS of surplus DNA from embryos classified as euploid by means of aCGH that ended up in miscarriage showed that 46% were euploid and the rest mosaic or polyploid (31). Using the same approach, we also found significantly more mosaic embryos in lost pregnancies than in ongoing pregnancies (P¼ .0062) (24).…”

Mosaicism: “survival of the fittest” versus “no embryo left behind”

“…In a recent study, blastocyst biopsy specimens from 46 embryos that had miscarried, which had originally been classified as euploid after aCGH, were reanalyzed using HR-NGS. Remarkably, over 50% were shown to be mosaic (4). These data suggest that mosaicism, undetectable by most PGD-A techniques, plays an important role in pregnancy loss.…”

“…Thus far, the proportion of embryos characterized as euploid using aCGH that can be shown to be mosaic by HR-NGS and additionally go on to produce a term pregnancy is 7% (5), but a larger data set will be needed to determine whether there are differences between mosaics associated with viable pregnancies and those that miscarry. Samples for the HR-NGS studies discussed earlier (4,5) were analyzed by Illumina MiSeq, with manual workflow, and software VeriSeq PGS 1 (Illumina), MCS 2.5, and BFMv4.1.…”

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

“…It has been determined that about 30 % of blastocysts are mosaic at the blastocyst stage [25,26]. However, it is important to realize that levels of mosaicism undetectable by current techniques may elevate this statistic and contribute more significantly to pregnancy loss than has been previously understood.…”