PGT Test Types Explained: PGT-A, PGT-M, and PGT-SR for International Patients in Thailand

Preimplantation genetic testing (PGT) is a group of laboratory tests performed on embryos created through in vitro fertilisation (IVF). The three main types are PGT-A, PGT-M, and PGT-SR. Each looks at a different kind of genetic or chromosomal question. PGT-A checks for extra or missing chromosomes across the embryo. PGT-M looks for a specific inherited condition known to run in a family. PGT-SR looks at chromosome rearrangements, such as translocations, that can affect how chromosomes are distributed. No PGT test guarantees a healthy pregnancy or a live birth, and not every patient needs PGT. The right choice, if any, is a medical decision made with your clinic based on your history and goals.

At a glance

• PGT-A — screens for extra or missing chromosomes (aneuploidy) across the embryo.
• PGT-M — tests for a specific inherited condition caused by a known gene variant in the family.
• PGT-SR — tests for chromosome structural rearrangements, such as translocations or inversions.
• All three require an IVF cycle and a biopsy of embryo cells.
• Results are reported as probabilities or classifications, not certainties.
• Test selection depends on your history, prior testing, and the reason PGT is being considered.

What PGT is and what it is not

PGT is a screening and diagnostic tool used during IVF. It is not a treatment for infertility, and it does not improve the quality of an embryo. It provides information that you and your clinician can use when deciding which embryo(s) to transfer, if any.

PGT is not a guarantee. A low-risk result does not promise a healthy baby, and a high-risk result does not always mean an embryo cannot produce a healthy pregnancy. Some results are uncertain, and some tests cannot detect every possible genetic condition. PGT also does not replace prenatal testing or newborn screening.

PGT-A: chromosome number screening

PGT-A (preimplantation genetic testing for aneuploidy) counts chromosomes. Human embryos should have 46 chromosomes in 23 pairs. An embryo with an extra or missing chromosome is called aneuploid. Aneuploidy becomes more common with increasing maternal age and is a common reason IVF cycles do not lead to a live birth.

PGT-A is usually considered when a clinic wants to estimate the chance that an embryo has a normal chromosome number. It may be discussed for patients with a history of recurrent implantation failure, recurrent pregnancy loss, or previous aneuploid pregnancies. It is also sometimes offered to patients without these histories, but the benefit in that situation is debated.

PGT-A cannot tell you whether an embryo will implant, and it does not test for single-gene conditions. It also cannot detect all chromosomal problems, such as very small deletions or duplications, unless a different test is used.

PGT-M: testing for a known inherited condition

PGT-M (preimplantation genetic testing for monogenic disorders) is used when a family is at risk of passing on a specific inherited condition caused by a change in a single gene. Examples include cystic fibrosis, spinal muscular atrophy, thalassaemia, and Huntington’s disease. The list of possible conditions is long, and the test must be customised for the gene variant in the family.

PGT-M usually requires a genetic counselling session and a DNA sample from one or both parents, and sometimes from an affected family member. The laboratory builds a specific test before the IVF cycle begins. This preparation can take time, so it is often started well before stimulation.

PGT-M does not screen for all genetic conditions. It only looks for the specific variant it was designed to detect. If the family variant is not known, additional genetic testing may be needed first.

PGT-SR: testing for chromosome rearrangements

PGT-SR (preimplantation genetic testing for structural rearrangements) is used when one parent has a chromosome rearrangement, such as a balanced translocation, Robertsonian translocation, or inversion. People with these rearrangements are often healthy, but they may produce embryos with unbalanced chromosome material, which can lead to miscarriage or a child with health problems.

PGT-SR is designed to identify embryos with unbalanced chromosome arrangements. Like PGT-M, it usually requires a custom laboratory setup and prior genetic testing of the parent(s) to characterise the rearrangement.

PGT-SR does not correct the rearrangement. It only helps select embryos that appear balanced or normal for the chromosomes involved. It cannot guarantee a healthy pregnancy.

How PGT-A, PGT-M, and PGT-SR compare

Feature	PGT-A	PGT-M	PGT-SR
What it looks at	Chromosome number (extra or missing chromosomes)	A specific gene variant linked to an inherited condition	Chromosome structure (rearrangements such as translocations)
Typical reason to consider	History of miscarriage, implantation failure, or advanced maternal age	Family history of a known single-gene condition	Known chromosome rearrangement in a parent
Preparation needed	Usually none beyond standard IVF	Genetic counselling, parental DNA, custom test design	Genetic counselling, parental DNA, custom test design
What it cannot do	Detect single-gene conditions or all structural problems	Detect conditions other than the one tested for	Correct the rearrangement or guarantee balance in all cells

This table is a general comparison. Your clinic may use different terms or combine tests. Some laboratories offer PGT-A and PGT-M together, or PGT-A plus PGT-SR, depending on the situation.

Why a clinic may recommend one test over another

Test selection is based on your medical and family history, previous genetic testing, and the reason PGT is being considered. For example:

• If you have a known balanced translocation, PGT-SR may be discussed.
• If you or your partner carry a gene variant for a serious inherited condition, PGT-M may be discussed.
• If you have recurrent pregnancy loss or repeated implantation failure without a known genetic cause, PGT-A may be discussed.
• If you have no specific risk factors, PGT may not be recommended at all.

Clinics may also consider factors such as the number of embryos available, the cost and time required for custom test design, and whether the laboratory has the necessary expertise. There is no single correct answer for everyone.

What PGT results can and cannot tell you

PGT results are usually reported as low-risk (sometimes called euploid or normal) or high-risk (aneuploid or affected). Some results are inconclusive, meaning the test could not give a clear answer. In some cases, a result may be affected by mosaicism, where an embryo has a mix of cells with different chromosome numbers. Mosaicism can make interpretation more complex.

A low-risk result does not guarantee a healthy baby. A high-risk result does not always mean the embryo cannot produce a healthy pregnancy, but it may reduce the chance. Your clinic should explain what your specific result means and what your options are.

Alternatives and limitations

PGT is one option among several. Alternatives include:

• IVF without PGT, with embryo selection based on appearance (morphology).
• Prenatal testing during pregnancy, such as chorionic villus sampling (CVS) or amniocentesis.
• Newborn screening after birth.
• Genetic counselling to understand risks without PGT.

PGT has limitations. It requires an embryo biopsy, which is an invasive procedure for the embryo. It adds cost and time to an IVF cycle. It may not be available for all conditions, and it cannot detect every genetic problem. Some embryos may be discarded or not transferred based on results that are later found to be inaccurate or uncertain.

Questions to ask your clinic

Before deciding on PGT, ask your clinic:

• Which PGT test are you recommending for my situation, and why?
• What will the test look for, and what will it not look for?
• How will the results be reported, and what do uncertain results mean?
• What are the alternatives to PGT in my case?
• What are the additional costs, and what do they cover?
• How long does test preparation take, and how does it fit with my travel plans?
• What are the risks of embryo biopsy?
• What happens to embryos that are not transferred?

Next steps for international patients

If you are considering PGT in Thailand, start by gathering your medical and genetic records. Ask your current doctor for a summary of your fertility history, any genetic test results, and relevant family history. Then contact a clinic that offers PGT and ask the questions above. You can also read more about international patient coordination, PGT in Thailand, our guides, and our FAQ.

Remember that PGT is a medical decision. This article is educational only and does not replace personalised advice from a qualified clinician.

Frequently asked questions

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

PGT-A screens for extra or missing chromosomes across the embryo. PGT-M tests for a specific inherited condition caused by a known gene variant in the family. PGT-SR tests for chromosome rearrangements, such as translocations, that can affect how chromosomes are distributed. Each test answers a different question, and a clinic may recommend one or more based on your history.

Do I need PGT if I am doing IVF?

Not necessarily. PGT is not required for IVF and is not appropriate for everyone. Whether PGT is useful depends on your medical history, family history, previous genetic testing, and the reason you are considering it. Your clinic can help you decide if PGT is right for your situation.

Can PGT guarantee a healthy baby?

No. PGT can provide information about the likelihood of certain chromosomal or genetic conditions, but it cannot guarantee a healthy pregnancy or a healthy baby. Some results are uncertain, and PGT does not detect every possible condition. Prenatal testing and newborn screening may still be recommended.

How long does PGT take, and does it affect my travel plans?

The time required depends on the type of PGT. PGT-A is usually performed as part of the IVF cycle, while PGT-M and PGT-SR often require custom test preparation that can take additional weeks before the IVF cycle begins. Ask your clinic for a timeline that fits your travel plans.

What should I ask a clinic in Thailand about PGT?

Ask which PGT test they recommend and why, what the test can and cannot detect, how results are reported, what the additional costs are, how long preparation takes, and what alternatives exist. Also ask about the experience and accreditation of the laboratory performing the test.

Continue your research

• International patient guide
• PGT in Thailand overview
• PGT and IVF guides

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.