Understanding PGT-A and PGT-M
If you are exploring IVF in Thailand, you may come across terms like PGT-A and PGT-M. Both are advanced genetic tests performed on embryos before transfer, but they answer different questions. PGT-A (Preimplantation Genetic Testing for Aneuploidy) checks whether an embryo has the correct number of chromosomes. PGT-M (Preimplantation Genetic Testing for Monogenic disorders) looks for a specific inherited genetic condition, such as cystic fibrosis or thalassemia. In short, PGT-A is a general screen, while PGT-M is a targeted test for a known genetic risk.
At a Glance: PGT-A vs PGT-M
- PGT-A: Screens for chromosomal abnormalities (aneuploidy) that may affect implantation or lead to miscarriage.
- PGT-M: Tests for a specific single-gene disorder that runs in the family.
- PGT-SR: A related test for structural rearrangements like translocations.
- Choice depends on your medical history: PGT-A is often considered for advanced maternal age or recurrent miscarriage; PGT-M is used when both partners are carriers of a genetic condition.
What Does PGT-A Test For?
PGT-A, formerly known as PGS, evaluates embryos for aneuploidy—having too many or too few chromosomes. Most embryos with aneuploidy fail to implant or result in miscarriage. By selecting embryos with the correct number of chromosomes, PGT-A may improve the chances of a successful pregnancy, especially for women over a certain age or those with recurrent implantation failure.
PGT-A does not test for specific genetic diseases. It is a general screen that looks at all chromosomes. It can identify conditions like Down syndrome (trisomy 21) but cannot tell you if an embryo carries a gene for a single-gene disorder.
What Does PGT-M Test For?
PGT-M is used when there is a known genetic condition in the family. It requires prior genetic testing of the parents to identify the specific mutation. PGT-M then checks embryos for that exact mutation, allowing transfer of embryos that do not carry the disorder.
PGT-M is often used for conditions like thalassemia, sickle cell anemia, cystic fibrosis, Huntington’s disease, and many others. It is also used for HLA matching (to create a sibling donor for an existing child with a condition like Fanconi anemia).
PGT-SR: A Related Test
PGT-SR (Preimplantation Genetic Testing for Structural Rearrangements) is used when one parent has a balanced translocation or other chromosomal rearrangement. This can cause embryos to have missing or extra chromosomal material, leading to miscarriage or birth defects. PGT-SR identifies embryos with normal or balanced chromosomes.
How Are PGT-A and PGT-M Performed?
Both tests require IVF. After eggs are fertilized, embryos are cultured for several days until they reach the blastocyst stage. A few cells are then biopsied from the trophectoderm (the part that becomes the placenta). The cells are sent to a genetics laboratory for analysis.
PGT-A uses techniques like next-generation sequencing (NGS) to count chromosomes. PGT-M uses PCR or other methods to detect the specific mutation. In some cases, PGT-A and PGT-M can be performed simultaneously on the same biopsy.
Which Test Is Right for You?
The choice between PGT-A and PGT-M depends on your medical history and reproductive goals. Here are some typical scenarios:
- PGT-A may be considered if: You are over a certain age (often 35 or older), have experienced recurrent miscarriage, have had repeated IVF failures, or have a history of chromosomal abnormalities in a previous pregnancy.
- PGT-M may be considered if: You or your partner are carriers of a single-gene disorder, you have a family history of a genetic condition, or you have a child with a genetic disorder and wish to avoid passing it on.
- PGT-SR may be considered if: You or your partner have a chromosomal rearrangement such as a translocation.
It is important to note that PGT is not a guarantee of a successful pregnancy or a healthy baby. Even with PGT, there is a small risk of misdiagnosis, and not all embryos that appear normal will implant. PGT is not recommended for everyone; your fertility specialist can help you weigh the benefits and limitations.
What Are the Limitations of PGT?
PGT-A and PGT-M have limitations. PGT-A cannot detect all genetic abnormalities, such as microdeletions or uniparental disomy. PGT-M is highly accurate but requires prior genetic testing of the parents. Both tests involve embryo biopsy, which carries a small risk of damage, though this is rare. Additionally, PGT does not eliminate the risk of miscarriage or birth defects entirely.
Cost Considerations in Thailand
The cost of PGT in Thailand varies depending on the clinic, the number of embryos tested, and whether you need PGT-A, PGT-M, or both. PGT-M is generally more expensive than PGT-A because it requires developing a customized test for your specific mutation. Costs may also include genetic counseling, biopsy, and laboratory fees. It is essential to ask your clinic for a detailed breakdown of costs and what is included.
Questions to Ask Your Clinic
Before deciding on PGT, consider asking your fertility specialist or clinic:
- What is the difference between PGT-A and PGT-M in your practice?
- Which test do you recommend for my situation, and why?
- What is the accuracy rate of your genetic testing?
- How many embryos typically survive the biopsy and testing process?
- What are the costs for PGT-A, PGT-M, and combined testing?
- How long does it take to receive results?
- Are there any additional tests or counseling required?
Next Steps
If you are considering PGT in Thailand, start by consulting with a fertility specialist who can review your medical history and recommend the appropriate testing. You may also want to speak with a genetic counselor to understand your risks and options. Once you have a clear picture, you can compare clinics and their PGT services.
For more information on PGT in Thailand, visit our PGT in Thailand page. You can also explore our guides and FAQ for additional insights.
Frequently asked questions
Can PGT-A and PGT-M be done together?
Yes, in many cases PGT-A and PGT-M can be performed on the same embryo biopsy. This allows you to screen for chromosomal abnormalities and test for a specific genetic disorder simultaneously. However, not all clinics offer combined testing, so you should confirm with your clinic.
Is PGT-M only for single gene disorders?
PGT-M is primarily used for single-gene disorders (monogenic conditions) such as cystic fibrosis, thalassemia, and Huntington's disease. It can also be used for HLA matching in certain situations. For chromosomal structural issues, PGT-SR is more appropriate.
How long does PGT testing take in Thailand?
The time for PGT results can vary by clinic and the type of test. Typically, PGT-A results may take a few days to a week, while PGT-M may take longer because a customized test needs to be developed. Your clinic will provide a specific timeline.
Does PGT guarantee a healthy baby?
No, PGT does not guarantee a successful pregnancy or a healthy baby. It reduces the risk of transferring embryos with certain genetic abnormalities, but there is still a small chance of misdiagnosis, and other factors can affect pregnancy outcomes.
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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.