Understanding Preimplantation Genetic Testing (PGT) in Thailand: PGT-A, PGT-M, and PGT-SR

Preimplantation genetic testing (PGT) is a set of techniques used during in vitro fertilization (IVF) to examine embryos for specific genetic or chromosomal conditions before transfer. In Thailand, PGT is available in many fertility clinics, but it is not a routine step for every patient. This guide explains the three main types of PGT—PGT-A, PGT-M, and PGT-SR—what they screen for, when they might be considered, and what to keep in mind when discussing options with your doctor.

At a Glance: The Three Types of PGT

• PGT-A (Preimplantation Genetic Testing for Aneuploidy): screens embryos for an abnormal number of chromosomes.
• PGT-M (Preimplantation Genetic Testing for Monogenic Disorders): screens for specific single-gene diseases, such as cystic fibrosis or thalassemia.
• PGT-SR (Preimplantation Genetic Testing for Structural Rearrangements): screens for chromosomal structural changes, such as translocations or inversions.

What Is PGT and Why Is It Used?

PGT is performed on embryos created through IVF. After fertilization, embryos are cultured in the laboratory for several days, and a small number of cells are biopsied for genetic analysis. The results help embryologists and doctors select embryos that are less likely to have certain genetic or chromosomal issues for transfer. The goal is to reduce the risk of miscarriage or the birth of a child with a specific genetic condition.

It is important to understand that PGT does not guarantee a successful pregnancy or a healthy baby. It is a screening tool that provides information to help you and your doctor make more informed decisions.

PGT-A: Screening for Chromosomal Number Abnormalities

PGT-A, formerly known as PGS (preimplantation genetic screening), checks embryos for aneuploidy—an abnormal number of chromosomes. Humans typically have 46 chromosomes in each cell, arranged in 23 pairs. An embryo with too many or too few chromosomes may fail to implant, lead to miscarriage, or result in a condition such as Down syndrome (trisomy 21).

PGT-A is often considered for patients who are of advanced maternal age, have experienced recurrent pregnancy loss, have had previous failed IVF cycles, or have a known chromosomal abnormality in one partner. However, the decision to use PGT-A is individual and should be discussed with your fertility specialist.

What PGT-A Can and Cannot Tell You

PGT-A can identify embryos with an abnormal number of chromosomes, but it cannot detect all genetic disorders. It also cannot guarantee that a transferred embryo will implant or result in a live birth. Some embryos with normal chromosomes may still fail to develop due to other factors.

PGT-M: Testing for Single-Gene Disorders

PGT-M is used when one or both partners are known carriers of a specific monogenic (single-gene) disorder. This test identifies embryos that have inherited the disease-causing mutation. Common examples include cystic fibrosis, sickle cell anemia, Tay-Sachs disease, and thalassemia, which is prevalent in Southeast Asia.

To use PGT-M, the specific genetic mutation must be identified in the parents. The test is then customized for each family. PGT-M can help couples who are at high risk of passing on a serious genetic condition to have children who are unaffected by that particular disease.

Important Considerations for PGT-M

PGT-M requires genetic counseling and often a preparatory workup to design the test. It is not available for all genetic conditions, and the accuracy depends on the specific mutation and laboratory protocols. As with all PGT, it does not eliminate the risk of other genetic or chromosomal issues.

PGT-SR: Testing for Chromosomal Structural Rearrangements

PGT-SR is designed for couples where one partner carries a structural chromosomal rearrangement, such as a balanced translocation or inversion. These rearrangements do not usually cause health problems in the carrier, but they can lead to embryos with unbalanced chromosomes, which may result in miscarriage or birth defects.

PGT-SR identifies embryos with a normal or balanced chromosomal arrangement, increasing the chance of a successful pregnancy and reducing the risk of miscarriage due to unbalanced chromosomes.

Who Might Consider PGT-SR?

PGT-SR is typically recommended for couples with a history of recurrent pregnancy loss, infertility, or a known chromosomal rearrangement in one partner. A genetic test called karyotyping is used to identify such rearrangements.

How PGT Is Performed in an IVF Cycle

If you and your doctor decide that PGT is appropriate, the process generally follows these steps:

1. Ovarian stimulation and egg retrieval: You undergo standard IVF treatment to produce and collect eggs.
2. Fertilization and embryo culture: Eggs are fertilized with sperm, and embryos are cultured for about five to six days until they reach the blastocyst stage.
3. Embryo biopsy: A few cells are removed from the outer layer of the embryo (trophectoderm) that will become the placenta. The biopsy is performed by an experienced embryologist.
4. Genetic analysis: The biopsied cells are sent to a genetics laboratory for testing. The type of PGT determines the specific analysis.
5. Embryo transfer: After results are available, one or more unaffected embryos are selected for transfer. Embryos that are not transferred may be frozen for future use.

The entire process adds time to an IVF cycle, as genetic testing may take several days to weeks. Your clinic will provide a timeline based on their laboratory arrangements.

Comparing PGT-A, PGT-M, and PGT-SR

Type	What It Screens For	Typical Candidates
PGT-A	Abnormal number of chromosomes (aneuploidy)	Advanced maternal age, recurrent miscarriage, repeated implantation failure, known chromosomal abnormality in a parent
PGT-M	Specific single-gene disorders (e.g., cystic fibrosis, thalassemia)	Couples who are carriers of a known monogenic disease
PGT-SR	Structural chromosomal rearrangements (e.g., translocations, inversions)	Couples with a known structural rearrangement in one partner, often with a history of miscarriage

Limitations and Risks of PGT

While PGT provides valuable information, it has limitations:

• Not diagnostic: PGT is a screening test, not a diagnostic test. There is a small risk of misdiagnosis, and a confirmatory prenatal test (such as amniocentesis or chorionic villus sampling) may be recommended after pregnancy is achieved.
• Embryo damage: The biopsy procedure carries a small risk of damaging the embryo, though this is rare when performed by experienced professionals.
• No guarantee: PGT does not guarantee a successful pregnancy or a healthy baby. Embryos with normal results may still fail to implant or miscarry due to other factors.
• Cost and time: PGT adds significant cost and time to an IVF cycle. It is not covered by all insurance plans, and the financial implications should be discussed with your clinic.

Alternatives to PGT

Depending on your situation, there may be alternatives to PGT. These include:

• Prenatal testing: After natural conception or IVF without PGT, you can undergo prenatal screening and diagnostic tests during pregnancy.
• Using donor gametes: If you are at high risk of passing on a genetic disorder, using donor eggs or sperm may be an option.
• Not testing: Some couples choose to proceed without PGT and accept the risk of a genetic condition.

Your fertility specialist and a genetic counselor can help you weigh these options based on your medical history and personal values.

Questions to Ask Your Clinic About PGT

If you are considering PGT in Thailand, here are some questions to ask your clinic:

• What types of PGT do you offer, and which one is recommended for my situation?
• How many embryos are typically biopsied, and what is the success rate of the biopsy procedure?
• How long does the genetic testing take, and how will it affect my IVF timeline?
• What is the cost of PGT, and are there any additional fees for genetic counseling or laboratory services?
• What is your laboratory’s accreditation and experience with PGT?
• How are embryos with inconclusive results handled?

Next Steps: Making an Informed Decision

Deciding whether to use PGT is a personal choice that should be made with the guidance of your fertility team. Here is a simple checklist to help you move forward:

1. Consult with a fertility specialist to discuss your medical history and fertility goals.
2. If PGT-M or PGT-SR is relevant, undergo genetic counseling and any necessary carrier screening or karyotyping.
3. Ask your clinic for detailed information about their PGT protocols, including laboratory standards and success rates (if available).
4. Consider the emotional, financial, and time commitments involved.
5. Make a decision that aligns with your values and medical needs.

For more information, explore our PGT in Thailand page, browse our guides, or check the FAQ section for common questions.

Frequently asked questions

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

PGT-A screens for an abnormal number of chromosomes (aneuploidy). PGT-M screens for specific single-gene disorders like cystic fibrosis or thalassemia. PGT-SR screens for structural chromosomal rearrangements such as translocations or inversions. Each test is used for different medical indications.

Is PGT mandatory for all IVF patients in Thailand?

No, PGT is not mandatory. It is an optional test that may be recommended based on your age, medical history, or genetic risk. Your fertility specialist will discuss whether PGT is appropriate for you.

Does PGT guarantee a healthy baby?

No, PGT does not guarantee a healthy baby. It is a screening tool that reduces the risk of transferring embryos with certain genetic or chromosomal issues, but it cannot eliminate all risks. A successful pregnancy and live birth depend on many factors.

How long does PGT take in an IVF cycle?

PGT adds time to an IVF cycle because embryos must be biopsied and sent to a genetics laboratory for analysis. The testing process can take several days to weeks, depending on the type of PGT and the laboratory's schedule. Your clinic will provide a specific timeline.

Are there risks associated with embryo biopsy for PGT?

Embryo biopsy is a delicate procedure that carries a small risk of damaging the embryo. However, when performed by experienced embryologists, the risk is low. There is also a small chance of misdiagnosis, so prenatal testing may be recommended after pregnancy.

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.