At a glance
Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR) can identify embryos with balanced or unbalanced translocations. This article explains how PGT-SR works, its availability in Thailand, and the steps involved in genetic counseling.
If you or your partner carry a balanced translocation, you may be concerned about the risk of passing on an unbalanced rearrangement to your children. Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR) is a technology designed to identify embryos with normal or balanced chromosomes, helping to select those with the best chance of developing into a healthy baby. In Thailand, PGT-SR is available at several fertility centers, but the specific techniques and protocols can vary. This article provides an overview of how PGT-SR works, its limitations, and the steps you should take when considering this option.
What Are Chromosomal Translocations?
A translocation occurs when a segment of one chromosome breaks off and attaches to another chromosome. If no genetic material is lost or gained, it is called a balanced translocation. Carriers of balanced translocations are usually healthy, but they have an increased risk of producing eggs or sperm with unbalanced chromosomes, which can lead to implantation failure, miscarriage, or a child with congenital anomalies. PGT-SR is specifically designed to detect these unbalanced rearrangements in embryos.
How Does PGT-SR Work?
PGT-SR is performed as part of an in vitro fertilization (IVF) cycle. After embryos are created in the lab, a few cells are biopsied from each embryo, usually on day 5 or 6 (blastocyst stage). The DNA from these cells is then analyzed using techniques such as next-generation sequencing (NGS) or array comparative genomic hybridization (aCGH). These methods can identify whether an embryo carries a normal, balanced, or unbalanced translocation. Only embryos with normal or balanced chromosomes are considered for transfer.
Availability of PGT-SR in Thailand
Several fertility clinics in Thailand offer PGT-SR, but the technology and expertise required are specialized. It is important to choose a clinic with experience in handling translocation cases. The cost of PGT-SR is typically higher than standard PGT-A (aneuploidy screening) because it requires more detailed analysis. You should confirm with the clinic whether they use NGS or aCGH, and whether they can detect your specific translocation type.
Genetic Counseling Steps
Before undergoing PGT-SR, genetic counseling is essential. A genetic counselor will review your translocation karyotype, explain the inheritance risks, and discuss the likelihood of producing normal embryos. They will also help you understand the limitations of PGT-SR, including the possibility that no normal embryos are available for transfer. After testing, the counselor will interpret the results and guide you in making informed decisions about embryo transfer or other options.
Limitations and Considerations
PGT-SR is a powerful tool, but it is not 100% accurate. There is a small risk of misdiagnosis due to technical limitations or mosaicism (when an embryo has both normal and abnormal cells). Additionally, PGT-SR cannot detect all types of translocations, especially if the breakpoints are in complex regions. It is also important to note that PGT-SR does not guarantee a pregnancy or a healthy child; it only reduces the risk of an unbalanced translocation. Some couples may choose to pursue prenatal diagnosis (amniocentesis or CVS) after a PGT-SR pregnancy to confirm the result.
Questions to Ask Your Clinic
- What specific technology do you use for PGT-SR (NGS or aCGH)?
- How many translocation cases have you handled?
- What is the expected success rate for obtaining normal embryos for my specific translocation?
- What are the costs involved, and are there any additional fees for genetic counseling?
- Do you offer follow-up genetic counseling after results?
Next Steps
- Obtain a detailed karyotype report from a geneticist.
- Schedule a consultation with a fertility clinic that offers PGT-SR.
- Meet with a genetic counselor to discuss risks and options.
- Decide whether to proceed with IVF and PGT-SR.
For more information, see our PGT in Thailand overview, guides, and FAQ.
Frequently asked questions
What is the difference between PGT-A and PGT-SR?
PGT-A screens for aneuploidies (abnormal number of chromosomes), while PGT-SR specifically detects structural rearrangements like translocations. PGT-SR requires more detailed analysis to identify balanced versus unbalanced rearrangements.
Can PGT-SR detect all types of translocations?
PGT-SR can detect most reciprocal and Robertsonian translocations, but its accuracy depends on the specific breakpoints and the technology used. Some complex rearrangements may not be detectable. A genetic counselor can advise on your specific case.
Is PGT-SR available at all fertility clinics in Thailand?
No, PGT-SR requires specialized laboratory expertise and equipment. Not all clinics offer it. You should confirm with the clinic whether they have experience with translocation cases and what technology they use.
What happens if no normal embryos are available after PGT-SR?
If all embryos are unbalanced, no transferable embryos may be available. Options include using donor eggs or sperm, considering adoption, or attempting another IVF cycle. Genetic counseling can help explore alternatives.
Do I need genetic counseling before PGT-SR?
Yes, genetic counseling is strongly recommended. It helps you understand the inheritance pattern, risks, and limitations of PGT-SR, and ensures you make an informed decision.
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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.
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