PGT-M vs PGT-A in Thailand: Which Genetic Test Should You Choose?

PGT-A and PGT-M: What’s the Difference?

Preimplantation genetic testing (PGT) is a set of techniques used to screen embryos created through IVF for genetic issues before transfer. Two common types are PGT-A and PGT-M. PGT-A (aneuploidy screening) checks for abnormal numbers of chromosomes, which can cause implantation failure or miscarriage. PGT-M (monogenic testing) looks for specific inherited single-gene disorders, such as cystic fibrosis or sickle cell anemia. In Thailand, both tests are available, but they serve different purposes. This guide explains the difference and helps you understand which test might be relevant for your situation.

At a Glance: PGT-A vs PGT-M

• PGT-A: Screens for chromosomal abnormalities (aneuploidy) in embryos.
• PGT-M: Tests for specific single-gene disorders that run in families.
• PGT-SR: A related test for structural rearrangements like translocations.
• Combination: Some patients may have both PGT-A and PGT-M to address multiple concerns.

What Is PGT-A?

PGT-A, previously known as preimplantation genetic screening (PGS), evaluates embryos for the correct number of chromosomes. Humans typically have 46 chromosomes. An embryo with missing or extra chromosomes is called aneuploid. Most aneuploid embryos fail to implant or result in miscarriage. PGT-A is often recommended for women of advanced maternal age, couples with recurrent implantation failure, or those with repeated pregnancy loss. It can also be used to reduce the risk of transferring an embryo with a chromosomal abnormality.

PGT-A does not test for specific diseases; it only checks chromosome number. It is not a guarantee of a healthy baby, but it can help select embryos with the highest chance of implantation.

What Is PGT-M?

PGT-M is designed for couples who carry a known genetic mutation for a single-gene disorder. If you or your partner have a family history of a condition like Huntington’s disease, thalassemia, or spinal muscular atrophy, PGT-M can identify embryos that do not carry the mutation. This test requires prior genetic analysis of the parents to design a personalized test for each embryo.

PGT-M is not a general screening tool; it is only useful when a specific genetic risk is already identified. It can be combined with PGT-A to also check for chromosomal abnormalities.

When Is Each Test Recommended?

Your fertility specialist may suggest PGT-A if you have:

• Advanced maternal age (typically over 35)
• Previous failed IVF cycles
• Recurrent miscarriage
• Severe male factor infertility

PGT-M may be recommended if:

• You or your partner carry a known single-gene mutation
• You have a family history of a genetic disorder
• You have had a child with a genetic condition

In some cases, both tests are used together. For example, a couple with a known genetic mutation and advanced maternal age might opt for both PGT-M and PGT-A to maximize the chance of a healthy pregnancy.

How Are the Tests Performed?

Both PGT-A and PGT-M require IVF. After eggs are fertilized, embryos are cultured for about five to six days until they reach the blastocyst stage. A few cells are then biopsied from the trophectoderm (the part that becomes the placenta). These cells are sent to a genetics laboratory for analysis. The biopsy is performed by an embryologist, and the process is similar for both tests.

The main difference is in the laboratory analysis. PGT-A uses techniques like next-generation sequencing (NGS) to count chromosomes. PGT-M uses polymerase chain reaction (PCR) or other methods to detect the specific mutation. The time to results may vary, but it typically takes a few days to a couple of weeks.

What Do the Results Mean?

For PGT-A, results are usually reported as:

• Euploid: normal chromosome number
• Aneuploid: abnormal chromosome number
• Mosaic: a mix of normal and abnormal cells

Euploid embryos are generally preferred for transfer. Aneuploid embryos are usually not transferred. Mosaic embryos may be considered, but this is a complex decision that should be discussed with your doctor.

For PGT-M, results indicate whether the embryo carries the specific mutation. Embryos without the mutation are considered unaffected and may be suitable for transfer. However, PGT-M does not eliminate all risks; it only tests for the specific disorder in question.

Limitations and Considerations

PGT is not a guarantee of a successful pregnancy or a healthy baby. Even with PGT-A, embryos can be mosaic, and some abnormalities may not be detected. PGT-M is highly accurate for the specific mutation tested, but it does not screen for other genetic conditions. Additionally, the biopsy process carries a small risk of embryo damage, though this is rare.

In Thailand, the availability and regulations for PGT may vary. It is important to choose a clinic with experience in genetic testing and to discuss the limitations with your specialist.

How to Choose Between PGT-A and PGT-M

The choice depends on your medical history and genetic risk. If you have no known genetic disorder, PGT-A may be more relevant. If you carry a specific mutation, PGT-M is necessary. In some cases, both tests are recommended. Your fertility doctor will guide you based on your individual situation.

Consider asking your clinic:

• What is your experience with PGT-A and PGT-M?
• How many embryos typically survive the biopsy process?
• What is the turnaround time for results?
• Are there any additional costs for genetic counseling?

Next Steps

If you are considering PGT in Thailand, start by consulting a fertility specialist. They can assess your medical history and recommend the appropriate testing. You may also want to seek genetic counseling to understand your risks and options. For more information, explore our PGT in Thailand guide and our general guides. If you have questions, check our FAQ section.

Frequently asked questions

Can PGT-A and PGT-M be done together?

Yes, PGT-A and PGT-M can be performed on the same embryo biopsy. This is often done when a couple has a known genetic mutation and also wants to screen for chromosomal abnormalities. The combined testing can provide more comprehensive information, but it may increase the cost and time required.

Is PGT-M only for couples with a known genetic disease?

Yes, PGT-M is specifically designed for couples who carry a known single-gene mutation. It is not a general screening test. If you do not have a known genetic risk, PGT-M is not typically recommended.

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

PGT-A screens for aneuploidy (abnormal chromosome numbers), while PGT-SR is used for structural rearrangements like translocations, where parts of chromosomes are swapped or missing. PGT-SR is less common and is recommended when a parent has a balanced translocation.

Does PGT guarantee a healthy baby?

No, PGT does not guarantee a healthy baby. It can reduce the risk of transferring embryos with specific genetic issues, but it cannot detect all potential problems. Other factors during pregnancy and after birth also affect a child's health.

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.