When embarking on fertility treatment, many people feel overwhelmed by the options of embryo genetic testing available. While some of those options will be essential, others, sometimes called ‘add-ons’ aren’t proven to benefit all patients, and can add unnecessary cost. Today, we shine a light on PGT-A (pre-implantation genetic testing for aneuploidy – previously known as pre-implantation genetic screening) in IVF. Here to help us understand what PGT-A is, and whether we might need it, is Access Fertility’s Medical Director, Prof Scott Nelson.
What is PGT-A?
Pre-implantation Genetic Testing for Aneuploidy, or PGT-A as thankfully it’s more commonly known, is a method we use for embyro genetic testing are normal, in terms of their number of chromosomes.
How does the test work?
A highly-skilled embryologist will perform a biopsy on the blastocyst at day 5, removing a few cells, which is tested for chromosomal abnormalities in the laboratory.
Why do I need to know about my embryo’s chromosomes?
As the HFEA explains “embryos with an abnormal number of chromosomes (known as aneuploid embryos) have less chance of developing into a baby or, less commonly, may result in a baby being born with a genetic condition”. By identifying an embryo which is chromosomally abnormal, we can reduce the risk of miscarriage and embryo loss that would likely result if it were transferred.
If the embryos test as ‘normal’, they’ll have a far higher chance of implanting and result in a live birth. In fact, a recent study shared at the American Society for Reproductive Medicine (ASRM) conference showed that out of 4,515 woman or couples who had up to three consecutive single embryo transfers of chromosomally normal embryos, 95% achieved a pregnancy.
Therefore, where pre-implantation genetic testing can be particularly helpful is in cases where patients are told their blastocysts are ‘beautiful’, and have a high rating, but they don’t implant. Rather than the patient wondering ‘what’s wrong with me’ and undergoing extensive, often invasive tests to understand why it didn’t implant, we can see whether it was likely due to the embryo itself.
Is PGT-A right for all women?
Since the risk of chromosomal abnormalities increases as the mother gets older, PGT-A is generally more useful to patients aged over 35. Of course, there are some rarer situations when it can also be useful to someone younger, for example, if they were at higher risk of having a baby with Down Syndrome.
The following chart shows the rising rate of chromosomal abnormality in embryos as the patients increase in age.
With this in mind, clinics will often discuss PGT-A testing to a patient aged 35 or over.
The HFEA has qualified PGT-A testing as ‘red’ on its traffic light system of ‘add ons’ (in its current form, which is currently under review). The reason for this is simply because it has not been proven that PGT-A can benefit all patients. If you are under 35 with no previous history of miscarriage or underlying condition that puts you at higher risk of chromosomal abnormality, it is unlikely that PGT-A will be needed.
What are the risks of PGT-A?
Significant development in the embryo genetic testing field have led to changes in the way embryologists perform PGT-A, reducing the risk to the embryo. Rather than performing the biopsy at day three, when there might just have eight cells to choose one from, embryologists now do the biopsy on day 5 or 6, when the embryo has 70-100 cells. As a result, when performed by a skilled embryologist, the PGT-A process is not detrimental to the embryo.
Having already collected the embryo, the process is entirely risk-free in a physical sense for the person undergoing fertility treatment. The only issue to bear in mind is that, while PGT-A is generally a very accurate technique, there are instances of a wrong result (it may miss an abnormality or detect one that isn’t there, meaning potentially viable embryos aren’t used).
How will performing a PGT-A impact my IVF journey?
As we mentioned above, since the embryo(s) already collected is the one (or ones) used for testing, there is no additional procedure required. However, it is worth noting that because testing takes place on day five blastocysts, and we are unable to get results immediately, you would need to have a frozen embryo transfer rather than a fresh cycle.
Is PGT-A included in the Access Fertility programs?
Because PGT-A is an additional, optional step that varies greatly in cost depending on the number of embryos you test, it is not covered in the Access Fertility programmes. However, it is compatible with our embryo genetic testing programmes, and you would simply pay the clinic directly for the additional cost.
What’s more, because PGT-A is compatible with our programmes, if after testing you discover the embryos are not viable, you would be able to move on to your next cycle straight away. This can be a huge benefit to some patients, wanting to avoid the time and heartache of implanting an embryo which is then unsuccessful.
Please note, if you’re planning on using PGT-A, you will be required to have a ‘freeze-all’, as all embryos will be frozen prior to the embryos being sent off for testing. This means that you would be required to pay the higher fee.
The one condition we have is that no ‘batching’ of embryos takes place. What this means is that any viable embryos from your first cycle would be tested and transferred prior to you moving on to your next egg collection.
Is PGT-A the only form of embryo genetic testing out there?
It’s the only form of genetic chromosome screening that’s readily available at present. However, there are other ways that we might observe potential issues. Even the classic embryo grading systems are likely to detect a problem (higher grade embryos are more likely to be chromosomally normal).
There are newer forms of non-invasive testing (i.e. which do not require a biopsy of the embryo), but these are still in trial and are not available in the UK right now.
PGT-M and PGT-SR are forms of Pre-implantation Genetic Testing which are looking for specific inherited genetic abnormalities that are known to occur within a family. Unfortunately PGD/PGT-M cannot be used alongside our programmes.