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Question 1

Is it possible to thaw a frozen embryo for PGT and freeze it later (after cell removal) for later transfer? Does the viability of the embryo decrease as a result of this?

Accepted Answer

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.

Question 2

Are frozen egg cells of the same quality as fresh ones? Are fertilisation and implantation rates of fresh and cryopreserved eggs comparable?

Accepted Answer

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.

Question 3

Is PGT the same as PGS and PGD?

Accepted Answer

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.

Question 4

Is there any work being done to determine the success rate of varying types of mosaicism?

Accepted Answer

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.

Question 5

Because PGT is such a new technique, how do we know it doesn’t carry risks that could manifest later in the child’s life?

Accepted Answer

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.

Question 6

Is there a relationship between egg quality and stimulation level?

Accepted Answer

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.

Question 7

What do you think of the new research that is being done on the fluid around the embryo rather than actual cells for PGT testing?

Accepted Answer

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.

Question 8

Do you anticipate PGT-A becoming a standard procedure in IVF?

Accepted Answer

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.

Question 9

What are the main reasons for implantation failure with euploid embryos?

Accepted Answer

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.

Question 10

Does genetic testing create “designer babies”?

Accepted Answer

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”.

Question 11

Do you think PGT can be valuable in IVF programs with donor eggs for patients who experienced implantation problems in the past?

Accepted Answer

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.

Question 12

Why do some aneuploid embryos implant and then miscarry? Why do they not all fail to implant?

Accepted Answer

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.

Question 13

What happens to aneuploid embryos?

Accepted Answer

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.

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