What Does PGT-A Test For? A Guide for Patients

PGT-A at a Glance

PGT-A stands for preimplantation genetic testing for aneuploidy. It is a test performed on embryos created through in vitro fertilization (IVF) before any embryo is transferred to the uterus. The purpose of PGT-A is to check whether an embryo has the correct number of chromosomes—the structures that carry your genes. Having too many or too few chromosomes is called aneuploidy, and it is a common reason why embryos fail to implant or miscarry.

PGT-A is not a test for specific genetic diseases, nor does it guarantee a successful pregnancy. Instead, it provides information that can help you and your fertility team decide which embryo to transfer first, potentially reducing the time it takes to achieve a healthy pregnancy.

What Does PGT-A Test For?

PGT-A screens for aneuploidy, meaning it checks the number of chromosomes in each embryo. Humans typically have 23 pairs of chromosomes, for a total of 46. An embryo with an abnormal number—such as an extra chromosome 21 (which causes Down syndrome) or a missing chromosome—is considered aneuploid.

Most aneuploidies are not compatible with life, and many embryos with these abnormalities stop developing before implantation or result in early miscarriage. PGT-A aims to identify embryos that have the correct number of chromosomes (euploid), which are more likely to implant and develop into a healthy baby.

It is important to note that PGT-A does not test for every possible genetic condition. It only looks at chromosome number, not structural changes or single-gene disorders. For those, other types of testing, such as PGT-M or PGT-SR, may be used.

How PGT-A Works

PGT-A is performed as part of an IVF cycle. After eggs are retrieved and fertilized in the laboratory, embryos are allowed to develop for about five to six days, until they reach the blastocyst stage. At that point, a small number of cells are removed from the part of the embryo that will become the placenta. This is called a biopsy.

The biopsied cells are then sent to a genetics laboratory, where they are analyzed for chromosome number. The process typically takes several days to a few weeks, depending on the laboratory and the specific technology used. Once results are available, your fertility team will discuss them with you and help you decide which embryo, if any, to transfer.

Because the biopsy removes cells from the placenta, not the baby, the procedure is considered safe for the embryo, though no medical procedure is without some risk. Your clinic can explain the specifics of their biopsy technique and the potential risks and benefits.

Who Might Consider PGT-A?

PGT-A is not recommended for everyone. It is often offered to people who have an increased risk of aneuploidy, such as:

• Women over the age of 35, as the risk of aneuploidy increases with maternal age.
• People who have experienced recurrent pregnancy loss or repeated implantation failure.
• Couples with a known chromosomal abnormality in one partner.
• People who have had previous pregnancies with a chromosomal condition.

However, the decision to use PGT-A is personal and should be made in consultation with your fertility specialist. Some people choose PGT-A to reduce the risk of miscarriage or to avoid the need for multiple transfer attempts. Others may not need it, especially if they are younger and have no known risk factors.

It is also worth noting that PGT-A is an optional test. You can choose to have IVF without PGT-A, and many people do. Your doctor can help you weigh the potential benefits and limitations based on your individual situation.

Understanding PGT-A Results

PGT-A results are typically reported as one of the following:

• Euploid: The embryo has the expected number of chromosomes. This is considered a normal result.
• Aneuploid: The embryo has an abnormal number of chromosomes. These embryos are generally not recommended for transfer, as they are less likely to result in a live birth.
• Mosaic: The embryo has a mix of normal and abnormal cells. Mosaic embryos may have a lower chance of implantation, but some can still lead to a healthy pregnancy. The decision to transfer a mosaic embryo is complex and should be discussed with your doctor.
• No result: Sometimes the test fails to produce a clear result, and the embryo may need to be retested or may not be suitable for transfer.

It is important to remember that a euploid embryo is not a guarantee of pregnancy. Other factors, such as the health of the uterus and the quality of the embryo, also play a role. PGT-A is a screening tool, not a diagnostic test, and it does not eliminate all risks.

What PGT-A Does Not Test For

PGT-A only checks for an abnormal number of chromosomes. It does not detect:

• Single-gene disorders, such as cystic fibrosis or sickle cell anemia. For these, PGT-M (preimplantation genetic testing for monogenic disorders) is used.
• Structural chromosomal rearrangements, such as translocations. For these, PGT-SR (preimplantation genetic testing for structural rearrangements) is used.
• All genetic conditions or birth defects. Many conditions are not detectable by any preimplantation test.

If you have a specific genetic condition in your family, your doctor may recommend PGT-M or PGT-SR instead of or in addition to PGT-A. These tests are more targeted and require prior genetic counseling and testing.

Limitations and Considerations

While PGT-A can provide valuable information, it has limitations that you should be aware of:

• It does not guarantee a live birth. Even a euploid embryo may fail to implant or miscarry for other reasons.
• It is not 100% accurate. There is a small chance of a false positive or false negative result.
• It adds cost and time to an IVF cycle. The biopsy and genetic analysis are additional procedures that may not be covered by insurance.
• It requires a laboratory with specialized expertise. Not all IVF clinics offer PGT-A, and the quality of testing can vary.

Before deciding on PGT-A, ask your clinic about their experience, the specific technology they use, and the success rates they have seen with PGT-A. Also, consider the emotional and financial costs, as well as the potential benefits.

Questions to Ask Your Clinic

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

• What is your experience with PGT-A? How many cycles have you performed?
• What is the cost of PGT-A, and what does it include?
• How long does it take to get results?
• What is your policy on transferring mosaic embryos?
• What are the risks of the biopsy procedure?
• How do you handle embryos with no result?

These questions can help you make an informed decision that aligns with your values and goals.

Next Steps

If you are new to PGT-A, start by learning more about the different types of preimplantation genetic testing. Our PGT in Thailand page provides an overview of PGT-A, PGT-M, and PGT-SR. You can also explore our guides for more in-depth information, or visit our FAQ section for common questions.

Ultimately, the decision to use PGT-A is a personal one. Take the time to discuss your options with your partner and your fertility specialist. They can help you understand how PGT-A fits into your overall treatment plan and whether it is right for you.

Frequently asked questions

What is the difference between PGT-A and PGT-M?

PGT-A screens embryos for an abnormal number of chromosomes (aneuploidy), while PGT-M tests for specific single-gene disorders, such as cystic fibrosis or Huntington's disease. PGT-A is often used to improve the chances of a successful pregnancy, whereas PGT-M is used when a couple is at risk of passing on a known genetic condition.

Is PGT-A necessary for all IVF patients?

No, PGT-A is not necessary for everyone. It is often recommended for women over 35, those with recurrent pregnancy loss, or couples with a known chromosomal abnormality. However, younger women with no known risk factors may not benefit significantly from PGT-A. Your fertility specialist can help you decide if PGT-A is appropriate for you.

Can PGT-A guarantee a healthy baby?

No, PGT-A cannot guarantee a healthy baby. It only screens for an abnormal number of chromosomes, which is one factor in embryo viability. Other genetic conditions, birth defects, and pregnancy complications are not detected by PGT-A. Even a euploid embryo may not result in a live birth.

What is a mosaic embryo?

A mosaic embryo has a mixture of cells with normal and abnormal chromosome numbers. This can happen when an error occurs during cell division after fertilization. Mosaic embryos may have a lower chance of implantation, but some can still lead to a healthy pregnancy. The decision to transfer a mosaic embryo is complex and should be discussed with your doctor.

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.