Robert Najdecki, MD, PhD
Co-Founder & Scientific Director at Assisting Nature , Assisting Nature – Human Reproduction & Genetics
Tatiana Chartomatsidou, MSc
Clinical Embryologist at Assisting Nature, Assisting Nature – Human Reproduction & Genetics
Category:
Embryo Implantation, Embryo Transfer, Genetics PGS / PGT-A, Miscarriages and RPL, Success Rates
Yes, it’s possible. The golden standard, however, is to fertilise egg cells into embryos and perform genetic testing on day 5 of their development – and then freeze them. This method provides the best results. Thawing and freezing an embryo, while possible, can skew the results of PGT testing, which is why we test embryos that way if there is no other way.
There is a small difference; as a rule, we prefer using fresh eggs. However, thanks to new vitrification techniques and time-lapse incubators, the results we get from using frozen eggs are very close to those we get from fresh ones.
PGS is the old name for the technique we now call PGT-A. There is also PGT-R, which also screens for aneuploidies, but in much smaller regions of chromosomes. PGD is another thing entirely; it stands for Pre-Implantation Genetic Diagnosis. Nowadays, it’s called PGT-M, because what it allows us to do is detect monogenic diseases – that is, diseases caused by a single gene.
Like we said before, we usually only transfer mosaic embryos as a last resort; not all embryos afflicted by mosaicism are transferrable. Whether or not we decide it’s viable depends on the percentage of mosaicism within the embryo, as well as what kind of abnormalities are implied. This is also a personalised issue with most patients, as we need an opinion of a geneticist in order to determine if a mosaic embryo can be transferred.
While PGT is an invasive technique, it is always performed by highly experienced embryologists. Because of this, there is basically no harm done to the embryo. Studies are still, of course, trying to determine if there are any effects of PGT testing. Because PGT testing uses cells from the outer embryo in the blastocyst stage – that is, not the cells that become the foetus – the risk of any damage is minimal. In fact, we would go as far as wagering that in five years, every IVF cycle will be done with PGT-A testing, as it provides us with a lot of information in case the transfer fails or the pregnancy ends with a miscarriage.
There is a relationship between the quality of the egg and the stimulation process. However, the precise impact of this relationship is age-dependant – younger patients, for instance, are not affected by it at all. In some older patients, however, egg quality may be adversely affected by large amounts of gonadotropins used in the stimulation process – which is why those patients are put on a personalised hormone regimen.
If the method turns out to be viable, it would be good news for all of us, as we’d have a non-invasive method of testing. It’s a very new idea and it remains to be seen if it’s something that could change PGT.
If it turns out testing embryo culture fluid delivers results as accurate and reliable as a biopsy, it would mean a revolution on the scale of NIPT – non-invasive prenatal testing. Like we said, however, this is all in the future – for now, we know too little about the technique to introduce it to embryology labs.
We have seen that PGT-A not only reduces the average length of treatment, it also increases all of the IVF success rates – clinical pregnancy rates, live birth rates, et cetera. It could be a standard part of IVF in the future, if for no other reason than to help clinics boast about their high success rates. However, currently there is a cost associated with testing, which prevents PGT-A from becoming a standard procedure.
Currently, we’re developing new protocols in which we strongly recommend PGT-A in case the first embryo transfer attempt fails.
There are many other factors involved in the process of implantation. Implantation failure can be caused by small anatomical variations in the uterus, endometrial stimulation, et cetera… Unfortunately, the human body is not a machine; in-depth testing is required to pinpoint the exact fault.
There is a lot of discussion whether or not genetic testing in IVF could lead to a “world of eugenics”. In my opinion, PGT-A is a clear and ethical procedure; in fact, knowingly creating embryos and pregnancies with chromosomal abnormalities is unethical and unacceptable. This isn’t eugenics or “baby designing”.
Yes. We advise our patients – if they are able to afford it, as it is an additional expense – to try PGT-A in donation cycles; even though our donors are all young and meet strict requirements, it’s still worth knowing whether the embryos are all euploid.
Some non-euploid embryos implant because they carry a chromosomal abnormality that may not be an issue during the implantation process. That same abnormality, however, may cause problems later, leading to a miscarriage. It all depends on which chromosome is affected.
Aneuploid embryos can’t be transferred, as they will not result in safe pregnancies. Embryos that are tested are stored until we receive the test results. Once we know which ones are aneuploid, the patient can decide whether the embryos get destroyed or donated for research.
Disclaimer:
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Contact details: The European Fertility Society C.I.C., 2 Lambseth Street, Eye, England, IP23 7AGAnalytical cookies are used to understand how visitors interact with the website. These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc.
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