PGT-A vs PGT-M vs PGT-SR: Which Genetic Test Is Right for Your IVF in Thailand

What Is Preimplantation Genetic Testing (PGT)?

Preimplantation genetic testing (PGT) is a set of techniques used to screen embryos created through in vitro fertilization (IVF) for genetic abnormalities before transfer to the uterus. PGT is performed on a few cells biopsied from an embryo at the blastocyst stage (typically day 5 or 6 of development). The goal is to help select embryos that are more likely to result in a healthy pregnancy, but it is important to understand that PGT does not guarantee a successful pregnancy or a healthy child. The three main types of PGT are PGT-A, PGT-M, and PGT-SR, each designed for different clinical scenarios.

PGT-A: Screening for Chromosomal Aneuploidy

What PGT-A Screens For

PGT-A (preimplantation genetic testing for aneuploidy) checks embryos for the correct number of chromosomes. A normal human cell should have 46 chromosomes (23 pairs). Aneuploidy—having too many or too few chromosomes—is a common cause of implantation failure, miscarriage, and conditions such as Down syndrome (trisomy 21). PGT-A identifies embryos with a normal chromosome count (euploid) versus those with an abnormal count (aneuploid).

Who Might Consider PGT-A

• Women of advanced maternal age (typically 35 and older), as the risk of aneuploidy increases with age.
• Couples with a history of recurrent miscarriage, which may be due to chromosomal abnormalities.
• Couples with repeated IVF implantation failure.
• Individuals with a known balanced translocation (though PGT-SR is more specific for structural rearrangements).
• Any patient who wishes to reduce the chance of transferring an aneuploid embryo, though it is not a guarantee.

Limitations of PGT-A

PGT-A cannot detect all genetic disorders, such as single-gene diseases (e.g., cystic fibrosis) or structural chromosomal rearrangements. It also cannot guarantee that a euploid embryo will implant or result in a live birth. Mosaicism—where an embryo has both normal and abnormal cells—can lead to ambiguous results. Additionally, the biopsy process carries a small risk of embryo damage, though this is low in experienced laboratories.

PGT-M: Testing for Single-Gene Disorders

What PGT-M Screens For

PGT-M (preimplantation genetic testing for monogenic disorders) is used to detect specific inherited single-gene conditions. This test is tailored to a particular genetic mutation known to run in a family, such as cystic fibrosis, Huntington’s disease, sickle cell anemia, or Tay-Sachs disease. PGT-M requires prior knowledge of the specific mutation and often involves creating a customized test for the couple.

Who Might Consider PGT-M

• Couples where one or both partners carry a known genetic mutation for a serious inherited disorder.
• Couples who have had a child with a genetic condition and wish to avoid passing it on.
• Individuals with a family history of a genetic disease who have undergone genetic counseling and testing.

Limitations of PGT-M

PGT-M is highly specific and cannot screen for other genetic abnormalities unless combined with PGT-A. The test development process can take weeks to months, and not all mutations are testable. PGT-M reduces but does not eliminate the risk of having an affected child; rare recombination events or technical errors can occur. Genetic counseling is essential before and after testing.

PGT-SR: Detecting Structural Chromosomal Rearrangements

What PGT-SR Screens For

PGT-SR (preimplantation genetic testing for structural rearrangements) is designed for individuals who carry a balanced structural chromosomal rearrangement, such as a translocation (where a piece of one chromosome attaches to another) or an inversion (where a chromosome segment is reversed). While carriers of balanced rearrangements are usually healthy, their embryos may inherit unbalanced rearrangements, leading to miscarriage or birth defects. PGT-SR identifies embryos with a normal or balanced chromosome structure.

Who Might Consider PGT-SR

• Couples where one partner is a known carrier of a balanced translocation or inversion.
• Couples with a history of recurrent miscarriage or infertility linked to a structural rearrangement.
• Individuals who have been diagnosed through karyotype testing.

Limitations of PGT-SR

PGT-SR cannot detect all types of chromosomal abnormalities; it focuses on the specific rearrangement. It may be combined with PGT-A for comprehensive screening. As with other PGT methods, there is a small risk of misdiagnosis, and not all embryos will be suitable for transfer.

How to Choose the Right Test

The decision between PGT-A, PGT-M, and PGT-SR depends on your medical history, genetic background, and reproductive goals. Here are some general considerations:

• If you have no known genetic condition but are concerned about age-related chromosomal abnormalities, PGT-A may be appropriate.
• If you or your partner carries a specific single-gene disorder, PGT-M is the test of choice, often combined with PGT-A.
• If you have a balanced translocation or inversion, PGT-SR is recommended, sometimes alongside PGT-A.
• If you have both a single-gene mutation and a structural rearrangement, a combination of tests may be possible.

It is essential to consult with a fertility specialist and a genetic counselor to determine which test—or combination of tests—is right for you. They will review your medical history, order necessary carrier screening or karyotyping, and explain the implications of test results.

PGT in Thailand: What to Expect

Thailand has become a popular destination for IVF with PGT due to its advanced medical facilities and competitive costs. Several fertility centers in Bangkok offer PGT services, including Deep & Harmonicare IVF Center (DHC), Bumrungrad International Hospital, Gift Fertility Clinic, Intrarat Hospital, PMG Hospital, and Prime Fertility Clinic. Each provider has its own laboratory capabilities, genetic testing partnerships, and pricing structures. It is important to verify directly with the clinic whether they offer the specific type of PGT you need, the turnaround time for results, and what is included in the quoted price.

PGT is typically performed on embryos created through IVF with intracytoplasmic sperm injection (ICSI) to avoid contamination from sperm cells. After biopsy, embryos are frozen (vitrified) while awaiting test results, which can take 1–2 weeks depending on the laboratory. A subsequent frozen embryo transfer (FET) is then scheduled.

Alternatives and Important Considerations

PGT is not the only option for genetic screening. Alternatives include:

• Prenatal diagnostic testing (chorionic villus sampling or amniocentesis) during pregnancy, which can confirm genetic abnormalities but carries a small risk of miscarriage.
• Non-invasive prenatal testing (NIPT), a blood test that screens for common aneuploidies but is not diagnostic.
• Carrier screening before conception to identify genetic risks.

PGT is an elective procedure and is not medically necessary for all patients. It does not guarantee a live birth or a healthy child, and there are ethical considerations regarding embryo selection. Discuss all options thoroughly with your healthcare team.

Frequently Asked Questions

Can PGT-A detect all genetic problems?

No, PGT-A only screens for the correct number of chromosomes. It does not detect single-gene disorders or structural rearrangements. For those, PGT-M or PGT-SR is needed.

Is PGT covered by insurance in Thailand?

Insurance coverage for PGT varies widely. Most international patients pay out-of-pocket. Check with your clinic and insurance provider for specific coverage details.

How long does PGT take?

After embryo biopsy, results typically take 1–2 weeks. The entire IVF cycle, including PGT and frozen embryo transfer, may take 2–3 months.

Does PGT harm the embryo?

The biopsy removes a few cells from the trophectoderm (future placenta), and studies suggest the risk of damage is low when performed by experienced embryologists. However, no procedure is risk-free.

Next Steps

If you are considering PGT as part of your IVF journey in Thailand, start by consulting with a fertility specialist and a genetic counselor. They can help you understand which test is appropriate based on your personal and family medical history. For more information, explore our PGT in Thailand guide, other guides, and FAQ section.

Frequently asked questions

Can PGT-A detect all genetic problems?

No, PGT-A only screens for the correct number of chromosomes. It does not detect single-gene disorders or structural rearrangements. For those, PGT-M or PGT-SR is needed.

Is PGT covered by insurance in Thailand?

Insurance coverage for PGT varies widely. Most international patients pay out-of-pocket. Check with your clinic and insurance provider for specific coverage details.

How long does PGT take?

After embryo biopsy, results typically take 1–2 weeks. The entire IVF cycle, including PGT and frozen embryo transfer, may take 2–3 months.

Does PGT harm the embryo?

The biopsy removes a few cells from the trophectoderm (future placenta), and studies suggest the risk of damage is low when performed by experienced embryologists. However, no procedure is risk-free.

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.