PGT for Chromosomal Abnormalities in Thailand: A Guide for Patients

What Is Preimplantation Genetic Testing (PGT)?

Preimplantation genetic testing (PGT) is a technique used during in vitro fertilization (IVF) to screen embryos for genetic or chromosomal abnormalities before transfer. It is not a guarantee of a healthy pregnancy or live birth, but it can help select embryos with a lower risk of certain conditions. In Thailand, PGT is available at several fertility centers, and the technology is broadly divided into three main types: PGT-A, PGT-M, and PGT-SR.

PGT-A: Testing for Aneuploidy

PGT-A (preimplantation genetic testing for aneuploidy) screens embryos for an abnormal number of chromosomes, known as aneuploidy. Humans typically have 46 chromosomes (23 pairs). An extra or missing chromosome can lead to conditions such as Down syndrome (trisomy 21) or Turner syndrome (monosomy X), and often results in implantation failure or miscarriage.

How PGT-A Works

During an IVF cycle, embryos are cultured for 5–6 days until they reach the blastocyst stage. A few cells are biopsied from the trophectoderm (the outer layer that becomes the placenta) and sent for genetic analysis. The embryo is then frozen while the results are processed. PGT-A uses techniques such as next-generation sequencing (NGS) or array comparative genomic hybridization (aCGH) to count the chromosomes.

Who Might Consider PGT-A?

PGT-A is often recommended for patients with:

• Advanced maternal age (typically 35 or older)
• Recurrent miscarriage (two or more pregnancy losses)
• Previous aneuploid pregnancy
• Severe male factor infertility
• Repeated IVF failure

However, not all patients need PGT-A. Younger patients with no history of miscarriage or genetic disorders may have a low risk of aneuploidy, and the added cost and procedure may not be justified. Discuss your individual risk factors with your fertility specialist.

Understanding PGT-A Results

Results are reported as:

• Euploid: Normal number of chromosomes. These embryos have the highest chance of implantation and a healthy pregnancy.
• Aneuploid: Abnormal number of chromosomes. These embryos are unlikely to result in a live birth and are typically not transferred.
• Mosaic: A mix of normal and abnormal cells. Mosaic embryos may have reduced potential, but some can still lead to healthy pregnancies. The decision to transfer a mosaic embryo should be made with genetic counseling.

It is important to note that PGT-A cannot detect all genetic disorders, and a euploid result does not guarantee a healthy baby.

PGT-SR: Testing for Structural Rearrangements

PGT-SR (preimplantation genetic testing for structural rearrangements) is designed for patients who carry balanced chromosomal rearrangements, such as translocations or inversions. These individuals have a normal total amount of genetic material but have chromosomes that are rearranged. While they are usually healthy, they are at increased risk of producing embryos with unbalanced rearrangements, which can lead to miscarriage or birth defects.

How PGT-SR Works

The process is similar to PGT-A: embryos are biopsied at the blastocyst stage, and the cells are analyzed to determine whether the chromosomal rearrangement is balanced or unbalanced. PGT-SR often uses the same technology as PGT-A (e.g., NGS) but with specialized analysis to detect the specific rearrangement.

Who Might Consider PGT-SR?

PGT-SR is typically offered to:

• Individuals or couples known to carry a balanced translocation or inversion
• Patients with recurrent miscarriage or a history of a child with an unbalanced rearrangement

If you have a known chromosomal rearrangement, genetic counseling can help you understand the risks and whether PGT-SR is appropriate.

Understanding PGT-SR Results

Results indicate whether the embryo has:

• Balanced (normal or balanced carrier): The embryo has a normal chromosome structure or carries the same balanced rearrangement as the parent. These embryos are suitable for transfer.
• Unbalanced: The embryo has extra or missing genetic material due to the rearrangement. These embryos are unlikely to result in a healthy pregnancy and are typically not transferred.

As with PGT-A, PGT-SR cannot detect all genetic issues, and a balanced result does not guarantee a healthy baby.

PGT-M: Testing for Monogenic Disorders

PGT-M (preimplantation genetic testing for monogenic disorders) is used to detect single-gene disorders such as cystic fibrosis, sickle cell disease, or Huntington’s disease. It is relevant for patients with a known genetic mutation in the family. PGT-M requires a custom test to be developed for each family, which takes time and additional cost. While not directly about chromosomal abnormalities, PGT-M may be combined with PGT-A or PGT-SR in some cases.

Limitations and Considerations

PGT is a powerful tool but has important limitations:

• Not 100% accurate: There is a small risk of misdiagnosis due to mosaicism, technical error, or contamination.
• Embryo biopsy risk: Although rare, the biopsy procedure may damage the embryo.
• No guarantee of pregnancy: Even a euploid embryo may fail to implant or miscarry due to other factors.
• Cost: PGT adds significant expense to an IVF cycle. In Thailand, costs vary by clinic and the number of embryos tested. Confirm exact pricing with your chosen clinic.
• Time: Testing takes several weeks, so embryos must be frozen and transferred in a subsequent cycle.

Alternatives to PGT

For some patients, alternatives may be considered:

• Prenatal testing: Chorionic villus sampling (CVS) or amniocentesis during pregnancy can diagnose chromosomal abnormalities, but these tests carry a small risk of miscarriage and cannot be used to select embryos.
• Donor eggs or sperm: Using gametes from a screened donor can reduce the risk of chromosomal abnormalities, especially in cases of advanced maternal age or known genetic disorders.
• Natural conception with genetic counseling: Some couples may choose to conceive naturally and undergo prenatal testing, accepting the risk of miscarriage or affected pregnancy.

Your fertility specialist can help you weigh the options based on your medical history and personal values.

What to Discuss with Your Clinic in Thailand

When considering PGT in Thailand, ask your clinic about:

• Which types of PGT are offered (PGT-A, PGT-SR, PGT-M)
• The laboratory’s experience and accreditation
• Costs for biopsy, testing, and embryo freezing
• Turnaround time for results
• Success rates for PGT cycles (note: these vary widely and should be interpreted cautiously)
• Genetic counseling services

For more information, see our PGT in Thailand overview, patient guides, and frequently asked questions.

Frequently asked questions

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

PGT-A screens for an abnormal number of chromosomes (aneuploidy), while PGT-SR detects unbalanced structural rearrangements like translocations. PGT-A is used for general aneuploidy risk, and PGT-SR is for patients with known balanced rearrangements.

Who should consider PGT for chromosomal abnormalities?

Patients with advanced maternal age, recurrent miscarriage, previous aneuploid pregnancy, or known chromosomal rearrangements may benefit. However, not everyone needs PGT; discuss your specific situation with a fertility specialist.

Can PGT guarantee a healthy baby?

No. PGT reduces the risk of transferring embryos with certain chromosomal abnormalities, but it cannot detect all genetic conditions, and there is still a chance of miscarriage or other complications.

How long does PGT take in Thailand?

After embryo biopsy, results typically take 1–2 weeks. Embryos are frozen while waiting, so transfer occurs in a later cycle. Confirm exact timelines with your clinic.

What are the risks of embryo biopsy?

The biopsy is generally safe, but there is a small risk of embryo damage or reduced viability. The procedure is performed by experienced embryologists to minimize risk.

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.