Understanding PGT-SR: A Guide for Patients with Structural Chromosomal Rearrangements

If you or your partner carry a balanced translocation or another structural chromosomal rearrangement, you may have heard about PGT-SR. This test is used during IVF to check embryos for an unbalanced set of chromosomes. It can help you understand which embryos may be less likely to implant or lead to a healthy pregnancy. This guide explains what PGT-SR is, when it is recommended, and how it differs from other types of preimplantation genetic testing.

What is PGT-SR?

PGT-SR stands for preimplantation genetic testing for structural rearrangements. It is a type of genetic test performed on embryos created through IVF. The test looks for changes in the structure of chromosomes, such as:

• Balanced translocations – when a piece of one chromosome has swapped with a piece of another, but no genetic material is lost or gained.
• Inversions – when a segment of a chromosome is reversed.
• Other structural changes that may affect how chromosomes pair up during cell division.

People who carry a balanced translocation often have no health problems themselves, but they may have a higher risk of producing embryos with unbalanced chromosomes. This can lead to implantation failure, miscarriage, or a child with a chromosomal disorder. PGT-SR aims to identify embryos that have a balanced set of chromosomes, which may be more likely to develop normally.

When is PGT-SR recommended?

PGT-SR is typically offered to couples where one partner is known to carry a structural chromosomal rearrangement. This may be discovered after:

• Recurrent miscarriages
• A previous pregnancy with an unbalanced chromosomal abnormality
• A child with a chromosomal disorder
• Infertility evaluation

It is not recommended for everyone. Your doctor may suggest PGT-SR if the risk of unbalanced embryos is significant. The decision depends on your specific rearrangement, your medical history, and your family planning goals.

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

PGT is an umbrella term for several tests. It is helpful to understand the differences:

Test	What it screens for	Typical use
PGT-A	Aneuploidy – extra or missing whole chromosomes	General screening for embryos, often for older mothers or repeated IVF failure
PGT-M	Specific single-gene disorders (e.g., cystic fibrosis, sickle cell)	Couples at risk of passing on a known genetic disease
PGT-SR	Structural rearrangements – unbalanced chromosomes due to translocations or inversions	Couples where one partner carries a structural rearrangement

PGT-SR is not the same as PGT-A. PGT-A looks at the number of chromosomes, while PGT-SR looks at the structure. Some clinics may combine PGT-SR with PGT-A to also check for aneuploidy, but this is not always necessary.

The PGT-SR process in Thailand

If you are considering PGT-SR in Thailand, the process generally follows these steps:

1. Consultation and genetic counseling: You will meet with a fertility specialist and a genetic counselor to review your medical history and discuss whether PGT-SR is appropriate.
2. IVF cycle: You will undergo ovarian stimulation and egg retrieval. The eggs are fertilized with sperm in the lab to create embryos.
3. Embryo biopsy: A few cells are removed from each embryo, usually on day 5 or 6 of development. This is done carefully to minimize harm to the embryo.
4. Genetic analysis: The cells are sent to a genetics laboratory for analysis. The lab uses techniques such as next-generation sequencing or array comparative genomic hybridization to detect structural rearrangements.
5. Embryo selection: Embryos that appear to have a balanced set of chromosomes are considered for transfer. Unbalanced embryos are usually not transferred.
6. Transfer and follow-up: A selected embryo is transferred to the uterus. Any remaining balanced embryos may be frozen for future use.

The entire process can take several weeks, but the exact timeline varies by clinic and your individual treatment plan.

What do PGT-SR results mean?

PGT-SR results are not always straightforward. Possible outcomes include:

• Balanced: The embryo has a normal or balanced set of chromosomes, similar to the carrier parent. These embryos are considered suitable for transfer.
• Unbalanced: The embryo has extra or missing chromosomal material. These embryos are usually not transferred because they may lead to miscarriage or a child with health problems.
• Inconclusive: The test did not provide a clear result. This can happen for technical reasons. You may need to discuss options with your doctor.

It is important to note that PGT-SR does not guarantee a pregnancy or a healthy baby. It is a screening tool that can help you make informed decisions.

Limitations and considerations

PGT-SR has limitations. It cannot detect all genetic conditions, and it does not eliminate the risk of miscarriage or birth defects. The biopsy and testing process may damage some embryos, although this is rare. Also, PGT-SR is not a substitute for prenatal testing during pregnancy.

In Thailand, the availability and regulations around PGT-SR may vary. Some clinics offer it as part of their genetic testing services, but not all. It is important to ask about the laboratory’s experience and the specific technology used.

Questions to ask your clinic in Thailand

Before deciding on PGT-SR, consider asking your clinic:

• What is your experience with PGT-SR for my type of rearrangement?
• Which genetic analysis method do you use, and what is the accuracy?
• How many embryos typically have a balanced result?
• What are the costs involved, and what is included?
• How long does the testing take, and how does it affect the IVF timeline?
• What are the options if no balanced embryos are available?

Next steps

If you are exploring PGT-SR in Thailand, start by gathering your medical records, including any previous genetic testing or karyotype results. Then, schedule a consultation with a fertility clinic that offers genetic testing. Bring your questions and ask for a clear explanation of the process, risks, and expected outcomes.

For more information on PGT in general, see our PGT in Thailand guide. You may also find our guides and FAQ sections helpful.

Frequently asked questions

Is PGT-SR the same as PGT-A?

No. PGT-A screens for aneuploidy (extra or missing whole chromosomes), while PGT-SR screens for structural rearrangements like translocations and inversions. They are different tests, though some clinics may combine them.

Who should consider PGT-SR?

PGT-SR is typically recommended for couples where one partner carries a structural chromosomal rearrangement, such as a balanced translocation. It may be suggested after recurrent miscarriages, a previous unbalanced pregnancy, or infertility evaluation.

Does PGT-SR guarantee a healthy baby?

No. PGT-SR is a screening tool that helps identify embryos with a balanced set of chromosomes. It does not guarantee pregnancy or a healthy child, and it cannot detect all genetic conditions.

What are the risks of PGT-SR?

The main risks are related to the IVF process and embryo biopsy. There is a small chance that the biopsy could damage the embryo, and the test may be inconclusive. It is important to discuss these risks with your doctor.

How much does PGT-SR cost in Thailand?

Costs vary widely depending on the clinic, the technology used, and your individual treatment plan. It is best to ask your clinic for a detailed breakdown of 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.