Understanding PGT-SR in Thailand: Structural Chromosomal Rearrangements and IVF

PGT-SR stands for preimplantation genetic testing for structural rearrangements. It is a laboratory test performed on embryos created through IVF to look for chromosome imbalances that can arise when a parent carries a structural chromosomal rearrangement, such as a translocation or inversion. It is not a treatment for the rearrangement itself, and it cannot guarantee a healthy pregnancy or child. Its purpose is to help identify embryos with a normal or balanced chromosome pattern so that those embryos can be considered for transfer. In Thailand, PGT-SR is offered within some IVF programmes, but availability, laboratory methods and eligibility criteria vary. Because the test is complex and its meaning depends on each person’s specific rearrangement, genetic counselling is a necessary first step, not an optional extra.

At a glance

• PGT-SR is designed for people who carry a known structural chromosomal rearrangement.
• It examines embryos created by IVF, not the parents’ chromosomes.
• It cannot detect every possible genetic or chromosomal condition.
• Genetic counselling before testing is strongly recommended to interpret what results can and cannot tell you.
• Costs, timelines and legal or documentation requirements in Thailand should be confirmed directly with the treating clinic and relevant authorities.

What is a structural chromosomal rearrangement?

Chromosomes are the packages of DNA inside our cells. Most people have 46 chromosomes, arranged in 23 pairs. A structural chromosomal rearrangement happens when a piece of one chromosome breaks off and attaches to another chromosome, or when a segment of a chromosome is reversed. Common types include translocations (where material is exchanged between chromosomes) and inversions (where a segment is flipped).

Many people who carry a rearrangement are healthy and may not know they have one until they experience recurrent pregnancy loss, infertility, or a child with a chromosome condition. This is because a balanced rearrangement — where no genetic material is missing or extra — often causes no health problems in the carrier. However, when that person makes eggs or sperm, the chromosomes may separate unevenly, leading to embryos with unbalanced chromosome patterns. Those embryos may fail to implant, lead to miscarriage, or result in a child with health or developmental concerns.

How PGT-SR differs from PGT-A and PGT-M

Preimplantation genetic testing is an umbrella term. The three main types answer different questions:

• PGT-A (aneuploidy screening) looks at the number of chromosomes in an embryo. It is sometimes used to screen for extra or missing chromosomes, often in the context of advanced maternal age or recurrent implantation failure. It does not specifically target a known rearrangement.
• PGT-M (monogenic disease) looks for a specific gene mutation that runs in a family, such as cystic fibrosis or spinal muscular atrophy.
• PGT-SR (structural rearrangement) is tailored to a known structural rearrangement in one or both parents. It aims to identify embryos with a balanced or normal chromosome pattern for the chromosomes involved in that rearrangement.

In practice, a clinic may combine PGT-SR with other tests, but the choice depends on the individual case. No single test covers everything.

Who might consider PGT-SR?

PGT-SR is generally discussed when a person or couple has a known structural chromosomal rearrangement and is undergoing IVF. Situations where it may be raised include:

• A carrier of a balanced translocation or inversion, confirmed by karyotype testing.
• A history of recurrent pregnancy loss where a parental rearrangement has been identified.
• Previous pregnancy or child with an unbalanced chromosome arrangement linked to a parental rearrangement.
• Infertility or difficulty conceiving in the context of a known rearrangement.

PGT-SR is not a routine test for all IVF patients. It is specific to the rearrangement found in the parents. Whether it is appropriate depends on the type of rearrangement, the chromosomes involved, the clinic’s laboratory capabilities, and the couple’s reproductive goals. A genetic counsellor or clinical geneticist can help clarify whether PGT-SR is a reasonable option and what alternatives exist.

The general PGT-SR process in Thailand

The exact steps vary by clinic, but the overall pathway usually follows this sequence:

1. Genetic counselling and confirmation of the rearrangement. Before IVF, a genetic counsellor reviews the karyotype report and family history. This step confirms the precise rearrangement and explains inheritance patterns, testing limitations, and alternatives.
2. IVF cycle. The patient undergoes ovarian stimulation, egg retrieval, and fertilisation in the laboratory to create embryos. This part is the same as standard IVF.
3. Embryo biopsy. When embryos reach a suitable stage, a few cells are removed from each embryo for testing. This is a laboratory procedure and does not usually harm the embryo’s development, though not all embryos will be suitable for biopsy.
4. Genetic analysis. The biopsied cells are analysed using methods designed to detect unbalanced chromosome patterns related to the specific rearrangement. The laboratory may use techniques such as microarray or next-generation sequencing, depending on the clinic.
5. Results and counselling. Results are discussed with the genetic counsellor and treating clinician. Embryos may be classified as balanced/normal, unbalanced, or sometimes inconclusive. Only embryos with a suitable result are considered for transfer.
6. Embryo transfer and follow-up. If a suitable embryo is available, it may be transferred to the uterus. Any pregnancy achieved should be monitored, and prenatal testing may be offered to confirm the baby’s chromosomes.

Timelines depend on the clinic’s laboratory schedule, the number of embryos, and whether embryos are frozen while awaiting results. Patients should ask the clinic for a realistic estimate for their situation.

What PGT-SR can and cannot tell you

PGT-SR can provide useful information about the chromosomes involved in the known rearrangement. However, it has important limitations:

• It does not test for all genetic conditions. A normal PGT-SR result does not rule out other chromosome problems, gene mutations, or health issues that arise during pregnancy.
• It cannot guarantee implantation, pregnancy, or a healthy child.
• Some embryos may give inconclusive results, and these are usually not transferred.
• The test’s accuracy depends on the laboratory’s methods and the specific rearrangement. Not every rearrangement can be reliably detected with the same approach.
• Mosaicism (where an embryo has a mix of normal and abnormal cells) can complicate interpretation.

These limitations should be explained during genetic counselling so that patients can make informed decisions.

Alternatives to PGT-SR

PGT-SR is one option among several. Alternatives may include:

• IVF without PGT-SR, with prenatal testing (such as chorionic villus sampling or amniocentesis) during pregnancy if a pregnancy occurs.
• Using donor eggs or donor sperm, which may avoid passing on the rearrangement, depending on the situation.
• Natural conception or other fertility treatments, with genetic counselling and prenatal diagnosis.
• Adoption or child-free living, which some people consider after weighing their options.

Each path has its own medical, emotional, and practical considerations. A genetic counsellor can help compare them without pressure.

Why genetic counselling is essential

Genetic counselling is not just a formality. It helps patients understand:

• The exact nature of the rearrangement and how it may be inherited.
• What PGT-SR can and cannot detect in their specific case.
• The possible outcomes of testing, including inconclusive results.
• Alternatives and their implications.
• Emotional and ethical aspects of embryo testing and selection.

In Thailand, genetic counselling services may be available at some IVF clinics or through referral. Patients should ask whether counselling is included, whether it is provided by a certified genetic counsellor or clinical geneticist, and whether interpretation is available in their language.

Practical questions to ask a clinic in Thailand

When exploring PGT-SR in Thailand, consider asking:

• Does your laboratory perform PGT-SR for my specific type of rearrangement?
• What testing method do you use, and what is its detection rate for my rearrangement?
• Who will provide genetic counselling, and is it included in the process?
• What are the costs for IVF, biopsy, testing, and counselling? Are there separate fees for freezing and storage?
• How long does it take to get results, and how are embryos stored in the meantime?
• What happens if all embryos are unbalanced or inconclusive?
• What documentation do I need as an international patient, and what are the current legal or regulatory requirements?
• Do you offer prenatal testing after a successful pregnancy?

Costs, legal requirements, and timelines are not fixed and can change. Confirm them directly with the clinic and, where relevant, with official Thai authorities or your own country’s embassy.

Next steps for international patients

If you are considering PGT-SR in Thailand, a sensible sequence is:

1. Gather your genetic test results, including the karyotype report and any relevant family history.
2. Speak with a genetic counsellor or clinical geneticist, ideally before contacting clinics, to understand your options.
3. Shortlist clinics that offer PGT-SR and ask the practical questions above.
4. Confirm costs, timelines, and documentation requirements in writing.
5. Plan travel and accommodation with flexibility, as IVF cycles can change.
6. Arrange follow-up care in your home country for monitoring and any prenatal testing.

PGT-SR is a specialised tool, not a guarantee. With careful counselling and realistic expectations, it can be part of a thoughtful approach to family building.

Frequently asked questions

Is PGT-SR the same as PGT-A?

No. PGT-A screens for extra or missing chromosomes across the embryo's chromosome set, often in the context of age-related risk. PGT-SR is tailored to a known structural rearrangement in a parent, such as a translocation or inversion. They answer different questions and are not interchangeable.

Can PGT-SR guarantee a healthy baby?

No. PGT-SR can identify embryos with a balanced or normal chromosome pattern for the specific rearrangement, but it cannot detect all genetic conditions, guarantee implantation or pregnancy, or ensure a child will be free of health issues. Prenatal testing may still be recommended during pregnancy.

Do I need genetic counselling before PGT-SR?

Yes, genetic counselling is strongly recommended. It confirms the exact rearrangement, explains inheritance and testing limitations, discusses alternatives, and helps you make an informed decision. Some clinics require it before proceeding.

What if all embryos are unbalanced or inconclusive?

If no suitable embryo is available for transfer, the clinic will discuss options such as another IVF cycle, using donor gametes, or other family-building paths. This is an important scenario to discuss with your genetic counsellor and clinician beforehand.

How much does PGT-SR cost in Thailand?

Costs vary widely depending on the clinic, the testing method, the number of embryos, and whether counselling, freezing, and storage are included. We do not publish specific prices because they change and depend on individual circumstances. Ask each clinic for a written breakdown of all fees.

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.