PGT-A

Chromosomes are genetic structures found in nearly every cell of our bodies. The first cell of an embryo is made up of a set of chromosomes from the sperm and another set from the egg. But if the cell doesn’t have the right number of chromosomes -  known as aneuploidy - this can lead to implantation failure, miscarriage or a baby affected with a genetic condition.

Pre-implantation genetic testing for aneuploidy (PGT-A), previously known as PGS testing, is a genetic screening test performed on embryos produced during an IVF treatment cycle. PGT-A gives information about your embryo's genetic health to help us select healthy embryos for transfer to improve your chance of achieving a successful pregnancy. 

Main benefits at a glance

Benefits exclusive to CARE patients

Fee information

Initial fee

Usually our embryologists choose embryos for transfer based on the way they look and develop. This certainly does work, but PGT-A lets us go deeper, allowing us to analyse the genetic makeup of embryos and check that they have the right number of chromosomes before they’re transferred to the womb.

By using PGT-A our embryologists can single out embryos with abnormalities before transfer. This improves IVF success rates for some patients and reduces the likelihood of miscarriage.

With PGT-A, each embryo will have one of four results

Euploid

This means the embryo is genetically balanced with 46 chromosomes. These embryos can be transferred.

Aneuploid

Aneuploid embryos aren’t genetically balanced and have too few, or too many, chromosomes. We won’t transfer these embryos, as they’re more likely to result in failed treatment or miscarriage.

Mosaic

Mosaic embryos have some cells that are euploid and some that are aneuploid. Depending on the chromosomes affected, we might still be able to transfer these embryos. If you have mosaic embryos we’ll offer you an appointment with a genetics counsellor to discuss your options further.

No result

In less than 5% of cases, we simply won’t be able to tell whether the embryo is euploid or aneuploid. These can still be transferred or, in special circumstances, they might be re-biopsied.

Could PGT-A be right for me?

If you’ve had treatment before that hasn’t worked, you’ve suffered miscarriages, or if you’re a woman in your mid–30s or older, we might recommend PGT-A; it could be that a chromosomal problem is the reason behind your failed treatments. Research suggests that more than 50% of human eggs have chromosomal problems and that this increases with age, so it’s thought to be the main reason older women can struggle to start or grow their families.

During your next cycle, we can use PGT-A to help us choose embryos with the right number of chromosomes for transfer, which could give you a better chance of success.

Patients in their first cycle who have suffered miscarriage previously or who are older than 35 may also wish to consider PGT-A.

Pre-implantation genetic testing has the potential to:

• PGT-A testing can identify the embryos with the correct number of chromosomes which are more likely to develop into a healthy baby. PGT-A testing can’t change the number of viable embryos available for transfer but, by transferring only those that have the correct number of chromosomes, the time taken to establish a pregnancy can be shorter and the misery of failed cycles and risks of miscarriage can be reduced.
• Where patients have undergone multiple rounds of IVF and have no explanation for the treatment failure, PGT-A testing can sometimes provide answers and help with decisions about future treatment options.
• CARE’s own data shows that by performing PGT-A and transferring euploid embryos clinical pregnancy rates (CPR) are increased. In the year to 30 September 2019 CPR per embryo transfer across patients of all ages following PGT-A was 49%[1] compared with 38% in non PGT-A cycles.[2]

[1] Based on 573 single euploid embryo transfers resulting in 281 pregnancies with a foetal heartbeat

[2] Based on 2645 embryo transfers resulting in 1016 pregnancies with a foetal heartbeat

HFEA Comment

Are there any risks associated with PGT-A?

There is a possible but unquantified risk that removing cells from an embryo may damage it and prevent it from developing. However, the first births following embryo biopsy for genetic screening were reported in 1990 and since then, thousands of children have been born, and health risks following embryo biopsy have not been identified as different from IVF/ICSI pregnancies in general.

The necessary freezing and thawing of embryos is highly successful with over 95% survival rate after thawing. There is however, a small risk that the embryo will not survive the process.

What is the evidence for PGT-A?

The independent regulator of fertility treatment, the Human Fertilisation and Embryology Authority (HFEA), has developed a ‘red-amber-green’ rating system and provides information on their website about treatments that are offered on top of your routine fertility treatment – known as treatment add-ons. They consider that the only way to be confident that a treatment is effective enough to be used routinely is to carry out a randomised controlled trial (RCT). In an RCT, patients are assigned randomly to two groups: a treatment group, given the new treatment and a control group, given a well-tried treatment or a placebo.

The HFEA has given PGT-A a red rating because it considers that there is no evidence from such trials that PGT-A increases the overall chances of having a baby. There is information on the HFEA website about PGT-A that you may find useful to consider.

CARE did participate in a large scale RCT called the STAR trial, which was published in December 2019. This trial concluded that there was a significant increase in pregnancy rate in a subset of women aged 35–40 where they had more than two embryos available for testing, although overall in all age groups there was no increase in ongoing pregnancy. However, we recognise that that more robust clinical and laboratory trials are needed to prove whether or not PGT-A significantly increases live birth rates. 

It is important to understand that PGT-A will not increase your overall chances of having a baby, although it may shorten your time to pregnancy by helping us select the best embryo sooner. For more information, please speak to your clinic team who will give you detailed patient information documents which outline all the relevant points about PGT-A, or you can visit the HFEA website. We also have some FAQs which you  might find helpful read our FAQs.

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