Understanding PGT Success for Chromosomal Abnormalities in Thailand

What Is PGT and How Does It Relate to Chromosomal Abnormalities?

Preimplantation genetic testing (PGT) is a technique used during in vitro fertilization (IVF) to screen embryos for genetic or chromosomal issues before transfer. For chromosomal abnormalities—such as aneuploidy (extra or missing chromosomes)—PGT-A (preimplantation genetic testing for aneuploidy) is the most common type. Other forms include PGT-M for monogenic disorders and PGT-SR for structural rearrangements. While PGT can reduce the risk of transferring an affected embryo, it does not guarantee a pregnancy or a healthy child. Success depends on multiple factors, including the quality of the embryo, the laboratory’s standards, and the timing of the biopsy.

At a Glance: Key Factors in PGT Success

• Embryo quality: Not all embryos survive biopsy or develop normally afterward.
• Lab standards: The experience of the embryology team and the technology used matter.
• Biopsy timing: Day 5 or 6 biopsy (blastocyst stage) is standard; earlier biopsy may be less reliable.
• Maternal age: Older eggs have higher rates of chromosomal abnormalities, affecting the number of usable embryos.
• Genetic counseling: Understanding results and limitations is essential before proceeding.

Factors That Affect PGT Success

Embryo Development and Biopsy Timing

PGT is typically performed on embryos that have reached the blastocyst stage (day 5 or 6 of development). Biopsy at this stage allows removal of a few cells from the trophectoderm (future placenta) without harming the inner cell mass (which becomes the fetus). Earlier biopsy (day 3) is less common and may have lower accuracy. Not all embryos reach the blastocyst stage, so the number available for testing can be limited.

Laboratory Quality and Experience

The success of PGT depends heavily on the laboratory’s ability to culture embryos to blastocyst, perform biopsy without damaging the embryo, and accurately analyze the genetic material. In Thailand, clinics may use different technologies (e.g., next-generation sequencing or array comparative genomic hybridization). Ask your clinic about their experience, success rates with PGT, and whether they have internal or external quality controls.

Maternal Age and Ovarian Reserve

Chromosomal abnormalities in embryos increase with maternal age. For women over 35, a higher proportion of embryos may be abnormal, reducing the number of embryos available for transfer after PGT. Younger women typically have more normal embryos, but PGT is not routinely recommended for all ages due to cost and the risk of discarding embryos that might self-correct or be mosaic.

Genetic Counseling and Informed Decision-Making

Before undergoing PGT, patients should receive genetic counseling to understand the implications of results, including the possibility of inconclusive findings, mosaicism (a mix of normal and abnormal cells), and the fact that PGT cannot detect all genetic conditions. Counseling helps set realistic expectations about success rates and the number of embryos needed.

What PGT Results Mean

PGT results classify embryos as:

• Euploid: Normal number of chromosomes, suitable for transfer.
• Aneuploid: Abnormal number of chromosomes, typically not transferred.
• Mosaic: A mix of normal and abnormal cells; transfer may be considered in some cases after counseling.

Even with a euploid embryo, implantation and live birth are not guaranteed. Other factors such as uterine receptivity, embryo quality, and overall health play a role.

Alternatives and Limitations of PGT

PGT is not the only option for addressing chromosomal abnormalities. Alternatives include:

• IVF without PGT: Embryos are selected based on morphology alone; some abnormal embryos may be transferred, but many will not implant or will miscarry early.
• Prenatal testing: Chorionic villus sampling or amniocentesis during pregnancy can detect chromosomal issues, but these are invasive and carry a small risk of miscarriage.
• Donor eggs or embryos: Using eggs from a younger donor can reduce the risk of chromosomal abnormalities.

Limitations of PGT include the cost, the possibility of no embryos being available for transfer, the risk of biopsy damaging the embryo, and the fact that PGT cannot detect all genetic or chromosomal problems (e.g., small deletions or duplications).

Questions to Ask Your Clinic About PGT

• What is your experience with PGT for chromosomal abnormalities?
• How many embryos typically reach the blastocyst stage for biopsy?
• What technology do you use for genetic analysis (e.g., NGS, aCGH)?
• How do you handle mosaic embryos?
• What are your success rates for live birth after PGT? (Note: clinics may report per embryo transfer or per cycle; ask for clarification.)
• What is the cost of PGT, and are there additional fees for biopsy, analysis, or embryo freezing?

Next Steps for Patients Considering PGT in Thailand

1. Consult with a fertility specialist to assess your individual situation, including age, ovarian reserve, and medical history.
2. Ask about the clinic’s PGT program, including lab standards and success rates.
3. Meet with a genetic counselor to understand the benefits, risks, and limitations of PGT.
4. Discuss the number of IVF cycles you may need to obtain a euploid embryo.
5. Consider the financial and emotional investment before proceeding.

For more information, explore our PGT in Thailand guide, other fertility guides, and frequently asked questions.

Frequently asked questions

Does PGT guarantee a healthy baby?

No. PGT reduces the risk of transferring an embryo with a chromosomal abnormality, but it cannot guarantee a pregnancy, live birth, or a child free from all genetic conditions. Some abnormalities may not be detected, and other factors affect pregnancy outcomes.

How many embryos are typically needed for PGT to be successful?

The number varies based on maternal age, ovarian reserve, and embryo development. Generally, having multiple embryos increases the chance of finding a euploid one. Your clinic can provide estimates based on your specific situation.

What is the success rate of PGT in Thailand?

Success rates depend on many factors, including the clinic's lab quality, patient age, and embryo quality. There is no single success rate. Ask your clinic for their live birth rates per embryo transfer after PGT, and compare with national averages if available.

Is PGT safe for the embryo?

PGT involves removing a few cells from the embryo. When performed by experienced embryologists at the blastocyst stage, the risk of damage is low. However, there is a small chance the embryo may not survive the biopsy or freezing process.

Can PGT detect all chromosomal abnormalities?

No. PGT-A screens for common aneuploidies (e.g., trisomy 21, 18, 13) and some structural changes, but it does not detect all genetic disorders, small deletions, or duplications. Discuss the scope of testing with your clinic.

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.