Cleavage of harm to the living embryo. By

Cleavage biopsy has a risk of amplification failure and high
rate of technical artefacts, and a high incidence of mosaicism and allele drop
out while TE biopsy suffers from a decrease rate of mosaicism. Further research
into the phenomenon of mosaicism is necessary to deal with the issue. The
comparison of TE biopsy strategy to previous ones strongly suggests that it is
the most promising approach in PGT (Danilo Cimadomo 2016). Another proposed
method of embryo selection by Poli et al is the investigation of the
application of proteomic measurements that could improve success rates in
clinical embryology. They describe a procedure that allows the identification
and quantification of proteins of embryonic origin, present in the blastocoel with
negligible risk of harm to the living embryo. By using targeted proteomics,
they demonstrated the feasibility of quantifying multiple proteins in samples
derived from single blastocoels and that such measurements correlate with
aspects of embryo viability, such as chromosomal (ploidy) status (Maurizio Poli
2015). An ideal outcome would be to bypass the embryo biopsy step and predict
euploidy and/or reproductive competence through non-invasive methods (Danilo
Cimadomo 2016). However, according to current trials in women undergoing ART,
there is insufficient evidence to show that metabolomics assessment of
embryos before implantation has any meaningful effect on rates of live birth,
ongoing pregnancy, or miscarriage rates. The existing evidence varied from very
low to low-quality (Siristatidis C. S. 2017). Also unfortunately, several
papers defined conventional parameters of embryo evaluation as just mildly
correlated with aneuploidy rate (Danilo Cimadomo 2016). Current technology
allows for test performance in the range of 98-99% accuracy (G. Harton 2010).
The patients should understand that a misdiagnosis is possible and the options
that are available to them should a pregnancy occurs, including prenatal
testing and genetic diagnosis (G. Harton 2010). The transfer of mosaic
aneuploid embryos has been reported to result in the occasional birth of
healthy children, but there is a great deal of uncertainty about the transfer
of such embryos and the circumstances and conditions for doing so (Ariel
Weissman 2017). The disadvantage of PND is that if the diagnosis shows the
fetus to be affected, the couple have to decide whether they wish to terminate
the pregnancy or carry on with the knowledge that their child is going to be
affected by the genetic disease (Dale 2011). However, these approaches expose
women to a high risk of miscarriage ranging between 1 and 3% (Danilo Cimadomo
2016). PGD offers some of these couples an alternative, as the diagnosis is
performed on the preimplantation embryo and only unaffected embryos are
transferred to the patient. The pregnancy is therefore initiated with the
knowledge that the fetus is free from the disease (Dale 2011). Over the last
several years, blastocyst biopsy with analysis of all chromosomes has
supplanted day 3 analysis via FISH (G. Harton 2010). Three randomized
controlled trials have shown a beneficial role of PGS using comprehensive
chromosome screening technology on TE cells. In general, PGS allows for a
decrease in embryo transfer number, higher implantation rates per transfer, and
a lower rate of miscarriage once implantation occurs for older patients
undergoing IVF (Mohamad Irani 2017). To finalise, PGT is an established
practice in IVF laboratories worldwide, however, there is a need to have a
regulated, standardised technique to ensure the embryos survival, viability and
productive potential is preserved. Cleavage stage biopsy remains the most
common method in Europe. Even though t has been found to have a negative impact
on embryo viability. TE biopsy is not such a widespread method but it is
increasing as several preclinical and clinical evidences recognise its value
and its advantages compared to cleavage and PB biopsy.  

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