At a glance
PGT-A is chromosome screening during IVF, not a guarantee. Learn who may be offered it, what it screens, and what it cannot detect.
PGT-A (preimplantation genetic testing for aneuploidy) is a laboratory test performed on a small sample of cells from an embryo created through IVF. It counts chromosomes to identify embryos with an abnormal number, such as an extra or missing chromosome. It does not diagnose a specific disease, measure embryo quality, or guarantee a pregnancy. In Thailand, as elsewhere, PGT-A is one option your fertility team may discuss, not a required step for every IVF cycle.
At a glance
- PGT-A screens for chromosome number, not for gene mutations or structural rearrangements.
- It is usually considered when the chance of chromosome errors is higher, but individual suitability is a clinical judgment.
- A “normal” result does not guarantee a healthy pregnancy or baby.
- An “abnormal” result does not always mean the embryo could never produce a pregnancy, but it does change the information available.
- Costs, timelines, and legal or documentation requirements vary and should be confirmed directly with your clinic and relevant authorities.
What PGT-A actually screens
PGT-A looks at the number of chromosomes in the embryo. Human embryos should have 46 chromosomes, arranged in 23 pairs. An embryo with an extra or missing chromosome is called aneuploid. Aneuploidy becomes more common with increasing maternal age, but it can occur at any age.
The test is typically done on a few cells removed from the trophectoderm, the outer layer of a blastocyst-stage embryo. The embryo itself is not changed by the biopsy. Results are reported as euploid (normal chromosome number), aneuploid (abnormal chromosome number), or sometimes mosaic (a mix of normal and abnormal cells). Some clinics also report a result as inconclusive, meaning the sample did not give a clear answer.
PGT-A does not look for single-gene disorders such as cystic fibrosis or Huntington’s disease. It does not look for structural chromosome rearrangements such as translocations. Those are addressed by different tests: PGT-M for monogenic disorders and PGT-SR for structural rearrangements. If you are considering PGT-A, it is worth asking your clinic which test is relevant to your situation.
Who may be offered PGT-A
PGT-A is not automatically recommended for everyone. Guidelines from professional fertility societies generally suggest it may be considered in specific circumstances, but they do not mandate it as a routine add-on for all IVF cycles. Your fertility specialist can explain whether it is likely to add useful information in your case.
Situations where PGT-A may be discussed include:
- Advanced maternal age. The chance of aneuploidy increases with age, so some clinics offer PGT-A to help select embryos for transfer.
- Recurrent pregnancy loss. If you have had multiple miscarriages, your doctor may suggest PGT-A as part of an evaluation, though it does not explain all causes of loss.
- Repeated implantation failure. When several IVF transfers have not led to a pregnancy, PGT-A may be considered, but evidence for its benefit in this situation is not uniform.
- Previous pregnancy with a chromosome abnormality. A prior aneuploid pregnancy may prompt a discussion about screening future embryos.
- Patient preference after counseling. Some people choose PGT-A to gain more information before transfer, even without a specific risk factor.
PGT-A is not a substitute for standard prenatal testing. It cannot replace ultrasound, blood tests, or diagnostic procedures during pregnancy. It also does not improve the quality of an embryo; it only provides information about chromosome number.
What PGT-A cannot tell you
Understanding the limits of PGT-A is as important as understanding its purpose. The test has several important limitations.
- It does not guarantee a pregnancy. A euploid embryo may still fail to implant or may result in a miscarriage for reasons unrelated to chromosome number.
- It does not guarantee a healthy baby. Many health conditions are caused by factors other than chromosome number, including gene mutations, environmental influences, and events during pregnancy.
- It does not detect all chromosome problems. Some small deletions or duplications, and some structural rearrangements, may not be seen with standard PGT-A.
- It can produce mosaic results. A mosaic result means the biopsy found a mix of cells with different chromosome numbers. The meaning of mosaicism is still an area of active research, and counseling can be complex.
- It can be inconclusive. Sometimes the sample does not yield enough DNA for a clear result.
- It does not measure embryo potential beyond chromosome number. Two embryos with the same chromosome result can have different developmental potential for reasons not captured by the test.
Because of these limits, PGT-A is best understood as one piece of information among many. It does not replace a thorough fertility evaluation or a discussion of all available options.
PGT-A compared with PGT-M and PGT-SR
PGT-A is part of a family of preimplantation genetic tests. Each has a different purpose.
| Test | What it looks for | Typical situation |
|---|---|---|
| PGT-A | Extra or missing chromosomes (aneuploidy) | Advanced maternal age, recurrent loss, repeated implantation failure, or patient preference |
| PGT-M | Specific single-gene disorders | Known inherited condition in the family |
| PGT-SR | Structural chromosome rearrangements | Known translocation or similar rearrangement |
If you have a known genetic condition in your family, PGT-M may be more relevant than PGT-A. If you carry a balanced translocation, PGT-SR may be discussed. Your clinic can help determine which test, if any, fits your situation.
Alternatives and additional considerations
PGT-A is not the only way to approach embryo selection. Some people choose to transfer embryos without PGT-A and rely on standard embryo grading, which looks at appearance under a microscope. Others may consider transferring a mosaic embryo after counseling, as some mosaic embryos can lead to healthy births. These decisions are highly individual and should be made with your fertility team.
It is also important to consider the practical aspects. PGT-A adds cost, requires embryo biopsy and freezing, and may extend the time to transfer. Not all embryos survive biopsy or thawing. These are not reasons to avoid PGT-A, but they are factors to weigh.
Questions to ask your clinic
If you are considering PGT-A in Thailand, asking clear questions can help you make an informed decision. Consider asking:
- What is the specific reason PGT-A is being recommended in my case?
- What are the alternatives, and what are their trade-offs?
- How does your laboratory handle mosaic or inconclusive results?
- What are the costs, including biopsy, testing, and embryo storage?
- What are the success rates for my age group and diagnosis at your clinic?
- What paperwork or legal requirements apply to me as an international patient?
- What happens to embryos that are not transferred?
These questions can help you understand the clinical and practical picture. They are not a substitute for personalized medical advice.
Next steps
If you are researching PGT-A, start by clarifying your own priorities and medical history. Gather any relevant records, such as previous IVF cycles, miscarriage history, or genetic test results. Then schedule a consultation with a fertility specialist who can review your situation and explain whether PGT-A is likely to be useful for you. You can also read more about PGT in Thailand and explore our guides for related topics. If you have general questions, our FAQ may help.
Remember that PGT-A is a tool, not a promise. It can provide useful information, but it cannot guarantee an outcome. A thoughtful discussion with your clinic is the best way to decide whether it fits your path.
Frequently asked questions
Does PGT-A guarantee a healthy baby?
No. PGT-A screens for chromosome number, but it cannot detect all genetic or health conditions. Many factors affect pregnancy and child health, and a euploid result does not guarantee a healthy baby.
Who is a candidate for PGT-A?
PGT-A may be discussed for people with advanced maternal age, recurrent pregnancy loss, repeated implantation failure, or a previous aneuploid pregnancy. Some people also choose it without specific risk factors. Suitability is a clinical judgment, so talk with your fertility specialist.
What is the difference between PGT-A, PGT-M, and PGT-SR?
PGT-A looks at chromosome number (aneuploidy). PGT-M looks for specific single-gene disorders. PGT-SR looks for structural chromosome rearrangements. Your clinic can help determine which test, if any, is relevant for you.
Can PGT-A detect all chromosome abnormalities?
No. PGT-A detects extra or missing whole chromosomes, but it may not detect small deletions or duplications, and some structural rearrangements may be missed. It also cannot detect gene mutations.
What does a mosaic PGT-A result mean?
A mosaic result means the biopsy found a mix of cells with different chromosome numbers. The implications are complex and still being studied. Your clinic can explain what a mosaic result might mean for your specific situation.
Continue your research
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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