What Is PGT-A and Why Is It Used in IVF?

PGT-A at a glance

PGT-A stands for preimplantation genetic testing for aneuploidy. It is a test that can be performed on embryos created through IVF before a pregnancy is established. The purpose is to check whether the embryo has the expected number of chromosomes. A normal human embryo should have 46 chromosomes. An embryo with missing or extra chromosomes is called aneuploid. Most aneuploid embryos do not implant or result in a miscarriage, but some can lead to conditions such as Down syndrome.

PGT-A is not a routine test for every IVF patient. It is offered as an optional screening tool to help select embryos that are more likely to be chromosomally normal. It does not guarantee a pregnancy or a healthy baby, and it does not test for all genetic conditions.

What does PGT-A screen for?

PGT-A screens for an abnormal number of chromosomes, known as aneuploidy. This includes conditions where there is an extra chromosome, such as trisomy 21 (Down syndrome), or a missing chromosome, such as Turner syndrome. It also detects larger structural changes in chromosomes, such as deletions or duplications, depending on the technology used.

It is important to understand that PGT-A does not test for single-gene disorders like cystic fibrosis or sickle cell anemia. Those require a different test called PGT-M.

How is PGT-A different from PGT-M?

PGT-M (preimplantation genetic testing for monogenic disorders) is used when one or both parents carry a known genetic mutation that could cause a specific inherited disease. PGT-M looks for that exact mutation in the embryo. PGT-A, on the other hand, is a broader screening test that checks chromosome number, not specific genes.

In some cases, embryos may be tested with both PGT-A and PGT-M. This is done when a couple has a known genetic condition and also wants to screen for chromosomal abnormalities. The two tests serve different purposes and are often used together.

Why is PGT-A used in IVF?

PGT-A is used for several reasons, depending on the patient’s history and age. Common reasons include:

• Advanced maternal age, as the risk of aneuploidy increases with age.
• Previous miscarriage, especially if it was due to a chromosomal abnormality.
• Repeated implantation failure, where embryos do not implant after several IVF attempts.
• Severe male factor infertility, which may be associated with higher rates of aneuploidy.
• To reduce the risk of transferring an embryo with a chromosomal abnormality.

It is important to note that PGT-A is not recommended for everyone. Some professional guidelines suggest that it may not improve live birth rates for all age groups. Your fertility specialist can help you understand whether PGT-A is appropriate for your situation.

What do PGT-A results mean?

PGT-A results are typically reported as:

• Euploid: The embryo has the expected number of chromosomes. This is considered a normal result.
• Aneuploid: The embryo has an abnormal number of chromosomes. This embryo is less likely to implant or develop normally.
• Mosaic: The embryo has a mix of normal and abnormal cells. The clinical significance is uncertain, and the embryo may or may not develop normally.
• No result: The test failed to produce a result, which can happen for technical reasons.

It is essential to discuss your results with a genetic counselor or your fertility doctor. They can explain what the results mean for your specific embryos and your chances of a successful pregnancy.

Limitations of PGT-A

PGT-A has limitations that you should be aware of:

• It does not guarantee a live birth or a healthy baby.
• It cannot detect all genetic conditions, such as single-gene disorders or structural abnormalities that are not related to chromosome number.
• It may not detect all cases of mosaicism, and the clinical impact of mosaicism is still being studied.
• The biopsy procedure itself carries a small risk of damaging the embryo, although this is rare.
• PGT-A is an additional cost and may not be covered by insurance.

Because of these limitations, PGT-A should be considered as one tool in the IVF process, not a guarantee.

Alternatives to PGT-A

If you are considering PGT-A, there are alternatives to discuss with your doctor:

• No testing: You may choose to transfer embryos without genetic screening, relying on embryo morphology (appearance) and other factors.
• PGT-M: If you have a known genetic condition, PGT-M may be more appropriate.
• Prenatal testing: You can opt for screening or diagnostic tests during pregnancy, such as non-invasive prenatal testing (NIPT) or amniocentesis.

Each option has its own benefits and risks. Your doctor can help you weigh them based on your medical history and preferences.

Questions to ask your clinic

If you are considering PGT-A, here are some questions to ask your fertility clinic:

• What is the cost of PGT-A, and what does it include?
• How many embryos are typically biopsied, and what is the success rate of the biopsy?
• How long does it take to get results?
• What is your policy on mosaic embryos?
• Do you offer genetic counseling as part of the process?

Next steps

If you are exploring PGT-A, consider these steps:

1. Consult with a fertility specialist to review your medical history and determine if PGT-A is appropriate.
2. Ask about the laboratory that will perform the testing and their accreditation.
3. Discuss the costs and whether any part is covered by insurance.
4. Consider genetic counseling to understand the implications of results.

For more information, you can explore our PGT in Thailand guide, visit our guides section, or check our FAQ page.

Frequently asked questions

Is PGT-A the same as PGS?

PGT-A was formerly known as PGS (preimplantation genetic screening). The name was changed to PGT-A to clarify that it screens for aneuploidy, not specific genetic disorders.

Does PGT-A improve IVF success rates?

PGT-A may help select embryos that are more likely to be chromosomally normal, which could reduce the risk of miscarriage and failed implantation. However, it does not guarantee a live birth, and its impact on overall success rates is still debated. Discuss your individual situation with your doctor.

Can PGT-A detect all genetic abnormalities?

No. PGT-A only screens for an abnormal number of chromosomes. It does not detect single-gene disorders, such as cystic fibrosis, or small structural changes. For those, PGT-M or other tests are needed.

Is PGT-A safe for the embryo?

PGT-A requires a biopsy of a few cells from the embryo. This is generally considered safe, but there is a small risk of embryo damage. The procedure is performed by experienced embryologists to minimize risks.

Continue your research

• PGT in Thailand overview
• PGT and IVF guides
• Frequently asked questions

Medical information notice: This article is educational and does not replace individual assessment, diagnosis, genetic counselling or treatment advice from a licensed clinician. Provider services, availability, fees and policies should be verified directly before booking.