PGT-A vs. PGT-M: Understanding Embryo Genetic Testing in Thailand

Preimplantation genetic testing (PGT) allows embryos created through IVF to be analyzed for genetic or chromosomal conditions before transfer. Two common types are PGT-A (for aneuploidy) and PGT-M (for monogenic disorders). While both involve embryo biopsy and genetic analysis, they answer different questions and are used in different clinical scenarios. This guide explains the purpose, process, and indications for each test, including when both may be recommended.

At a Glance: PGT-A vs. PGT-M

• PGT-A screens embryos for an abnormal number of chromosomes (aneuploidy), such as trisomy 21 or monosomy X. It is often used to improve implantation rates and reduce miscarriage risk, especially in older mothers or those with recurrent pregnancy loss.
• PGT-M tests for specific single-gene disorders (e.g., cystic fibrosis, Huntington’s disease, thalassemia) when one or both parents carry a known mutation. It aims to select embryos free of that particular condition.
• PGT-SR (structural rearrangements) is a related test for embryos from parents with balanced translocations or inversions, often grouped with PGT-A in discussion.
• Both tests require IVF with embryo biopsy, usually on day 5 or 6 (blastocyst stage), and involve a short period of embryo freezing while analysis is completed.

What Is PGT-A?

PGT-A (preimplantation genetic testing for aneuploidy) evaluates embryos for the correct number of chromosomes. Humans typically have 23 pairs (46 total). An extra or missing chromosome (aneuploidy) is a common cause of implantation failure, miscarriage, and conditions like Down syndrome. PGT-A identifies which embryos are euploid (normal chromosome count) and which are aneuploid. It does not detect single-gene disorders or small genetic changes.

Who Might Consider PGT-A?

• Women of advanced maternal age (typically over 35)
• Couples with recurrent pregnancy loss
• Repeated IVF implantation failure
• Previous pregnancy with a chromosomal abnormality
• Severe male factor infertility

Limitations of PGT-A

• It cannot detect all genetic conditions, only large chromosomal gains or losses.
• Mosaicism (a mix of normal and abnormal cells in the embryo) can lead to uncertain results.
• It does not guarantee a successful pregnancy or live birth.
• Embryo biopsy carries a small risk of damage, though modern techniques minimize this.

What Is PGT-M?

PGT-M (preimplantation genetic testing for monogenic disorders) looks for a specific genetic mutation known to cause a hereditary disease. It requires prior knowledge of the mutation in the parents. The test is customized for each family, often using linkage analysis or direct mutation detection. PGT-M can dramatically reduce the risk of having a child affected by a serious genetic condition.

Who Might Consider PGT-M?

• Couples where one or both partners carry a mutation for an autosomal dominant disorder (e.g., Huntington’s disease, Marfan syndrome)
• Carriers of autosomal recessive conditions (e.g., cystic fibrosis, sickle cell disease, spinal muscular atrophy)
• X-linked disorders (e.g., Duchenne muscular dystrophy, hemophilia)
• Couples with a family history of a known genetic condition

Limitations of PGT-M

• It only tests for the specific mutation(s) requested; other genetic or chromosomal issues are not assessed unless combined with PGT-A.
• Test development can take weeks to months and requires genetic information from both parents and sometimes other family members.
• Not all embryos may be free of the mutation; the chance of having a transferable embryo depends on inheritance patterns.
• It does not eliminate the possibility of other genetic or health problems.

When Are Both PGT-A and PGT-M Used?

In some cases, a couple may benefit from both tests simultaneously. For example, a woman over 35 who carries a BRCA1 mutation might want PGT-M to select embryos without the mutation and PGT-A to identify chromosomally normal embryos. Combined testing can be performed on the same biopsy sample, though it adds to the complexity and cost. Discuss with your clinic whether dual testing is appropriate for your situation.

Key Differences at a Glance

Feature	PGT-A	PGT-M
What it detects	Chromosomal aneuploidy (extra/missing chromosomes)	Specific single-gene mutations
Indication	Age, recurrent loss, implantation failure	Known genetic disorder risk
Customization	Standardized test	Family-specific test development required
Results	Euploid, aneuploid, mosaic	Affected, unaffected, or inconclusive
Time for results	Typically 1–2 weeks	May take longer due to test setup
Cost	Varies by clinic; confirm directly	Generally higher due to customization

Questions to Ask Your Clinic

• What is the biopsy technique used (day 5 trophectoderm biopsy)?
• How many cells are taken, and what is the risk of embryo damage?
• How long does it take to receive results?
• Can PGT-A and PGT-M be performed together on the same biopsy?
• What is the cost for each test, and are there additional fees for transport or storage?
• What happens to embryos with inconclusive or mosaic results?
• Is genetic counseling available before and after testing?

Next Steps

1. Consult with a fertility specialist and genetic counselor to determine if PGT is appropriate for your situation.
2. If considering PGT-M, arrange for carrier screening or confirm known mutations with your doctor.
3. Choose a clinic experienced in PGT and discuss their laboratory protocols and success rates (note: success rates vary and should be interpreted cautiously).
4. Review the legal and ethical framework for PGT in Thailand, as regulations may affect which conditions can be tested.
5. Plan for the additional time and cost involved in PGT cycles.

For more information, explore our PGT in Thailand guide, other patient guides, and frequently asked questions.

Frequently asked questions

Can PGT-A and PGT-M be done at the same time?

Yes, both tests can be performed on the same embryo biopsy sample. This is often called combined PGT. However, it requires a laboratory capable of both analyses and may increase the overall cost and time for results. Discuss with your clinic whether combined testing is suitable for your case.

Does PGT-A guarantee a healthy baby?

No. PGT-A only screens for chromosomal aneuploidy; it does not detect all genetic disorders, birth defects, or health conditions. A euploid embryo still has a risk of other problems. PGT-A can improve the chances of a successful pregnancy but does not guarantee a healthy child.

Is PGT-M available for all genetic conditions?

PGT-M can be developed for most single-gene disorders where the specific mutation is known. However, test development may not be feasible for very rare conditions or when family genetic samples are unavailable. Your clinic and genetic counselor can advise on feasibility.

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

PGT-SR (structural rearrangements) is used when a parent carries a balanced translocation or inversion. It detects embryos with unbalanced chromosomal rearrangements, which can cause miscarriage or birth defects. PGT-A screens for aneuploidy, while PGT-SR focuses on structural changes. Some laboratories combine both.

How long does it take to get PGT results?

Results typically take 1–2 weeks for PGT-A and may take longer for PGT-M due to the need for test customization. The exact timeline depends on the laboratory and whether combined testing is performed. Embryos are frozen while awaiting results.

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.