Pre-implantation genetic testing for aneuploidy (PGT-A)

Chromosomes are cellular structures that carry genetic information (DNA) and are found in every cell of the body, including embryo cells. Each cell has 46 chromosomes, while egg and sperm cells have 23. When an egg and sperm merge and create an embryo, they each contribute their 23 chromosomes with genetic material to the embryo creating new cells with 46 chromosomes. 

As the embryo cells divide, many errors involving chromosomes can occur, such as too many, or too few, chromosomes, or missing or added pieces of DNA. When a cell doesn’t have the right number of chromosomes it is known as aneuploidy. This can lead to embryo implantation failure or miscarriage. For this reason, PGT-A can help you select the best quality embryo that minimises these risks. 

What is PGT-A?

Pre-implantation genetic testing for aneuploidy (PGT-A) is a genetic test for embryos performed during fertility treatment, such as in vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI). It involves checking the embryo cells for an abnormal number of chromosomes, which would indicate that the embryo may fail to implant or miscarry. These embryos are usually not transferred back into the womb during fertility treatment. 1

How is PGT-A done?

PGT-A is usually carried out on day 5 or 6 of embryo development in the lab when an embryo has developed into a blastocyst. By this time, the blastocyst embryo has two distinct structures called the inner cell mass (which becomes a human body) and trophectoderm (which becomes placenta). Trophectoderm is an outer layer that surrounds the blastocyst with the inner cell mass being on the inside of the blastocyst.

Using a special, very fine pipette, a few cells are taken from the trophectoderm by a highly skilled embryologist. These cells are packaged in a sterile lab environment and sent to a specialist genetics lab to get tested. The embryo is then frozen until the PGT-A results are available in a few weeks and, depending on the result, transferred by frozen embryo transfer (FET). 1

What are the results of PGT-A?

• Euploid - the embryo cells have 46 chromosomes and should be transferred. 

• Aneuploid - too few or too many chromosomes have been found in the embryo cells and therefore should not be transferred as they are likely to result in a failure of implantation or miscarriage.

• Mosaic - some embryos can have some cells that carry 46 chromosomes and some that carry fewer or more than 46. Mosaicism is identified in approximately 20-30% of cases. 2

Who should be recommended to have PGT-A?

The patients that may benefit from PGT-A remains a topic of debate. Your doctor will be able to discuss this with you and may recommend you to opt-in for PGT-A as part of your IVF cycle if you have:

• Recurrent pregnancy loss/miscarriage

• Recurrent implantation failure 

• For women of advanced maternal age, as they are at a higher risk of creating genetically abnormal embryos

Does PGT-A increase the success of IVF?

If you fall into the recommendation category mentioned above, PGT-A will most likely increase your chances of success per embryo transfer, but not overall, as the test itself will not improve the quality of the embryos. PGT-A can help indicate that the embryo being transferred has the correct number of chromosomes and has a lower chance of implantation failure and miscarriage. 

Another benefit of PGT-A is that it can decrease the overall cost of fertility treatments. While PGT-A itself is costly, it may reduce the number of cycles needed and the time to become pregnant. This way, choosing to perform PGT-A can reduce the time to pregnancy and cost of treatment. 

The Human Fertilisation and Embryology Authority has PGT-A under ‘red’ in their add-on traffic light rating list. This means that there is no scientific evidence from randomised controlled trials that shows that PGT-A effectively improves pregnancy outcomes. 

Is PGT-A safe for the embryos?

​​PGT-A involves removing a few cells from an embryo which has a small risk of causing damage to the embryo which may prevent it from developing once it has been transferred back into the womb. However this risk is low as only the most highly skilled embryologists perform PGT-A testing and studies have shown that the removal of cells from the blastocyst doesn’t harm the embryo’s development.

If you would like to have PGT-A in your IVF or ICSI fertility treatment, you should speak to your doctor. At Apricity, we work with a trusted network of first-class clinics, doctors and embryologists who are hand-selected and screened, so you are always in good hands. They will help you to make an informed decision regarding PGT-A and the rest of your treatment.

If you’d like to start your treatment, you can do so by booking a free call with one of our fertility advisors.