PGT-A vs PGT-M: How to Choose the Right PGT Test in Thailand

PGT-A and PGT-M are different tests used for different reasons. PGT-A checks embryos for extra or missing chromosomes and is usually considered when age or repeated implantation failure raises concern about chromosomal number. PGT-M looks for a specific inherited condition that runs in your family. Neither test guarantees a healthy pregnancy or a live birth, and neither is right for everyone. In Thailand, the test you choose should follow a clinical assessment, genetic counselling where relevant, and a clear discussion of what the result can and cannot tell you.

At a glance

• PGT-A screens for chromosomal number (aneuploidy) across the embryo.
• PGT-M targets a known single-gene or familial condition.
• PGT-SR is a related option when a parent carries a structural chromosome rearrangement.
• PGT-M usually requires a prior genetic diagnosis and may need family DNA or a probe build.
• Both tests are performed on a few cells removed from an embryo, usually at the blastocyst stage.
• Results are reported as probabilities or classifications, not certainties.

What each test is designed to do

PGT-A (preimplantation genetic testing for aneuploidy) counts chromosomes. It estimates whether an embryo has the expected number of chromosomes or an abnormal number, such as trisomy or monosomy. It does not read the full DNA sequence and does not rule out all genetic conditions.

PGT-M (preimplantation genetic testing for monogenic disorders) looks for a specific gene change that is known to cause a condition in your family. It is used when there is a confirmed diagnosis, such as cystic fibrosis, spinal muscular atrophy, thalassaemia, or another inherited condition. Because the target is specific, the laboratory needs to know exactly what it is looking for before testing begins.

PGT-SR (for structural rearrangements) is a third category. It is considered when a parent has a balanced translocation, inversion, or similar chromosome rearrangement. It is mentioned here because it is often discussed alongside PGT-A and PGT-M, but it is a separate test with its own indications.

Side-by-side comparison: indications, lab steps, and decision triggers

Feature	PGT-A	PGT-M
Main question	Does this embryo have the expected number of chromosomes?	Did this embryo inherit the specific familial gene change?
Typical indications	Advanced maternal age, repeated implantation failure, recurrent pregnancy loss, or a history of chromosomal abnormality in a prior pregnancy.	A known inherited condition in the family, a confirmed carrier status in one or both parents, or a prior affected child.
What the lab needs first	Embryo biopsy sample; no prior family testing is usually required.	A confirmed genetic diagnosis, the exact gene change, and often DNA samples from family members to build a test probe.
Laboratory steps	Embryo culture to blastocyst, trophectoderm biopsy, cell preparation, whole-genome amplification, then chromosome analysis.	Embryo culture to blastocyst, trophectoderm biopsy, cell preparation, whole-genome amplification, then targeted analysis for the known gene change.
Result format	Classification such as euploid, aneuploid, mosaic, or inconclusive.	Affected, unaffected, carrier, or inconclusive, depending on the condition and test design.
Main limitations	Does not detect all genetic conditions; mosaicism and inconclusive results can occur; does not guarantee implantation or live birth.	Requires a known target; probe development can take time; does not screen for unrelated chromosomal conditions unless combined with PGT-A.
Decision trigger	Age-related risk, repeated loss, or prior aneuploid pregnancy.	Family history, carrier status, or a known diagnosis that could be passed on.

How the laboratory process differs

Both tests begin the same way. The embryo is cultured, usually to day 5 or 6, and a small number of cells are removed from the outer layer (trophectoderm). The cells are prepared and their DNA is amplified so there is enough material to analyse.

From there, the paths diverge. PGT-A uses a genome-wide method to estimate chromosome number. PGT-M uses a targeted method designed around the specific gene change in your family. For PGT-M, the laboratory often needs to build a custom probe, which can require blood or saliva samples from you, your partner, and sometimes a family member. This preparation step can add time before the embryo testing itself can be done.

Some clinics offer combined testing when both chromosomal number and a specific familial condition are concerns. Whether this is appropriate depends on your history and the laboratory’s capabilities, and it should be discussed with your clinician.

Understanding results and uncertainty

PGT results are not always a simple yes or no. PGT-A can report a mosaic result, meaning the embryo has a mix of cells with different chromosome numbers. The clinical meaning of mosaicism is still an area of active research, and clinics may handle mosaic embryos differently. An inconclusive result can also occur when the sample does not provide enough information.

PGT-M results are usually clearer for the specific condition being tested, but they still do not guarantee a healthy child. They tell you whether the embryo inherited the gene change the test was designed to find. They do not rule out other genetic conditions, pregnancy complications, or health issues unrelated to the tested gene.

No PGT test can guarantee implantation, pregnancy, live birth, or child health. Your clinic should explain the detection rate, the chance of an inconclusive result, and what a result would mean for your transfer decisions.

Alternatives and when testing may not be needed

PGT is not a required step for every IVF cycle. Some patients choose to transfer untested embryos, especially when there is no clear indication and the number of available embryos is limited. Others use donor gametes, genetic counselling, or prenatal testing instead of, or in addition to, PGT.

For some families, the more important first step is genetic counselling to clarify the actual risk and the options available. A genetic counsellor can help you understand whether PGT-M is technically possible, what the test can detect, and what the alternatives are.

Questions to ask your clinic in Thailand

• Based on my history, which PGT test—if any—do you recommend, and why?
• What are the indications you are using to make that recommendation?
• For PGT-M, what preparation is needed, and how long does probe development take?
• How do you report mosaic or inconclusive results, and what are my options then?
• What are the costs of the test, the biopsy, and any additional laboratory work?
• What is your policy on transferring untested or mosaic embryos?
• Do you provide genetic counselling, or can you refer me to a counsellor?
• What documents or consent forms will I need to provide?

Next-step checklist

1. Gather your personal and family medical history, including any prior genetic test results.
2. Ask your clinic whether genetic counselling is available before you decide.
3. Clarify which test is being recommended and what question it answers.
4. Ask about laboratory timelines, especially if PGT-M probe development is needed.
5. Request a written summary of costs, including biopsy, testing, and storage fees.
6. Confirm how results will be explained and what happens if the result is inconclusive.
7. Review the clinic’s consent process and any legal or travel requirements with the clinic directly.

Choosing between PGT-A and PGT-M is not a matter of one test being better than the other. They answer different questions. The right choice depends on your medical history, your family’s genetic information, and what you hope to learn. Start with a clinical assessment and a clear conversation about what each test can and cannot do. For more context, see our PGT in Thailand overview, browse the guides, or check the FAQ.

Frequently asked questions

Can I have PGT-A and PGT-M at the same time?

Sometimes, yes. Combined testing may be possible when both chromosomal number and a specific familial condition are concerns. Whether it is appropriate depends on your history, the laboratory's methods, and the quality of the embryo sample. Your clinic can explain whether combined testing is available and what it would involve.

Do I need PGT-M if no one in my family has a genetic condition?

PGT-M is designed for a known inherited condition. If there is no known condition, there is usually no target for the test. A genetic counsellor can help clarify whether any testing is indicated based on your personal and family history.

What does a mosaic result on PGT-A mean?

A mosaic result means the embryo has a mix of cells with different chromosome numbers. The clinical significance is still being studied, and clinics may have different policies about transferring mosaic embryos. Ask your clinic how they interpret and report mosaicism.

Does PGT guarantee a healthy baby?

No. PGT can provide information about specific chromosomal or genetic findings, but it cannot guarantee implantation, pregnancy, live birth, or child health. It does not detect every possible genetic condition. Your clinic should explain the limitations for your situation.

How long does PGT-M take compared to PGT-A?

PGT-M often requires additional preparation, such as building a custom probe, which can add time before testing. PGT-A does not usually require this step. Exact timelines vary by laboratory and should be confirmed with your clinic.

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.