At a glance
Understand the differences between PGT-A and PGT-M, when each is used, and how to decide which test—or both—may be right for your IVF journey in Thailand.
What Are PGT-A and PGT-M?
Preimplantation genetic testing (PGT) is performed on embryos created through in vitro fertilization (IVF) before transfer to the uterus. Two common types are PGT-A and PGT-M.
- PGT-A (Preimplantation Genetic Testing for Aneuploidy) screens embryos for abnormal numbers of chromosomes (aneuploidy). It helps identify embryos with the correct chromosome count (euploid), which may have a higher chance of implantation and lower risk of miscarriage due to chromosomal errors.
- PGT-M (Preimplantation Genetic Testing for Monogenic Disorders) detects specific single-gene disorders, such as cystic fibrosis, sickle cell disease, or Huntington’s disease. It is used when one or both parents carry a known genetic mutation.
A third type, PGT-SR (Preimplantation Genetic Testing for Structural Rearrangements), identifies embryos with balanced or unbalanced chromosomal rearrangements, such as translocations. This article focuses on PGT-A and PGT-M, as they are the most commonly discussed.
Key Differences in Purpose and Technique
| Aspect | PGT-A | PGT-M |
|---|---|---|
| Purpose | Screen for chromosome number abnormalities | Detect specific single-gene disorders |
| Who needs it | Often recommended for advanced maternal age, recurrent miscarriage, repeated implantation failure, or severe male factor infertility; also used for any patient wanting to reduce aneuploidy risk | Couples known to carry a genetic mutation for a serious inherited condition |
| Technique | Biopsy of 5–10 cells from the trophectoderm (future placenta) on day 5/6; analyzed by next-generation sequencing (NGS) or array comparative genomic hybridization (aCGH) | Same biopsy method; then uses polymerase chain reaction (PCR) or other mutation-specific methods to test for the known mutation |
| Result | Euploid (normal), aneuploid (abnormal), or mosaic (mixed cell lines) | Affected, unaffected (carrier or non-carrier), or inconclusive |
| Limitations | Cannot detect all genetic disorders; mosaicism can complicate interpretation; does not guarantee pregnancy or live birth | Requires prior knowledge of the specific mutation; test must be custom-developed for each family; may have technical limitations |
When Are Both PGT-A and PGT-M Needed?
In some cases, a couple may benefit from both tests. For example:
- A woman of advanced maternal age who also carries a BRCA1 mutation may want PGT-A to reduce aneuploidy risk and PGT-M to select embryos without the mutation.
- A couple with a history of recurrent miscarriage and a known single-gene disorder may use PGT-A to identify chromosomally normal embryos and PGT-M to avoid the inherited condition.
When both tests are performed, the embryo biopsy is the same, but the genetic analysis includes both aneuploidy screening and mutation detection. This is often called combined PGT or PGT-A+PGT-M.
Example Scenarios
Scenario 1: Advanced Maternal Age
A 40-year-old woman with no known genetic disorders may choose PGT-A to select euploid embryos, potentially improving implantation rates and reducing miscarriage risk. PGT-M is not needed.
Scenario 2: Known Genetic Mutation
A couple where both partners are carriers of cystic fibrosis may opt for PGT-M to identify embryos that are unaffected. If the female partner is under 35 with no fertility issues, PGT-A may not be necessary, though some clinics offer it as an optional add-on.
Scenario 3: Both Indications
A 38-year-old woman who carries a mutation for Huntington’s disease may choose both PGT-A and PGT-M to maximize the chance of a healthy pregnancy.
How to Decide: Questions to Discuss With Your Doctor
Choosing between PGT-A and PGT-M—or deciding to use both—requires careful counseling. Consider asking your fertility specialist and genetic counselor:
- What is my risk of having an embryo with a chromosomal abnormality or a specific genetic disorder?
- Does my age, medical history, or family history suggest a benefit from PGT-A?
- Have I or my partner been tested for carrier status of common genetic conditions?
- What are the success rates and limitations of each test at the clinic I am considering?
- How will the results affect embryo transfer decisions?
- What are the costs and timelines for each test?
Remember that PGT does not guarantee a pregnancy or a healthy baby. It is a screening tool that can reduce certain risks but cannot eliminate all possibilities of genetic or chromosomal conditions.
Alternatives and Additional Considerations
For patients who do not wish to undergo PGT, alternatives include:
- Prenatal testing (chorionic villus sampling or amniocentesis) during pregnancy to diagnose chromosomal or genetic conditions.
- Non-invasive prenatal testing (NIPT) for common aneuploidies, though it is a screening test, not diagnostic.
- Donor eggs or sperm to avoid passing on genetic disorders.
- Natural conception with or without carrier screening and prenatal diagnosis.
Each option has its own benefits, risks, and limitations. A genetic counselor can help you weigh these choices based on your personal values and medical situation.
Next Steps
If you are considering IVF with PGT in Thailand, start by consulting a fertility clinic that offers comprehensive genetic testing services. Ask about their experience with PGT-A and PGT-M, the laboratory they use, and the counseling support available. For more information, explore our PGT in Thailand overview, guides, and FAQ.
Frequently asked questions
Can PGT-A detect all genetic disorders?
No, PGT-A only screens for abnormal numbers of chromosomes. It does not detect single-gene disorders or structural rearrangements. For specific genetic conditions, PGT-M or PGT-SR is required.
Is PGT-M always necessary if I am a carrier of a genetic mutation?
Not necessarily. If the condition is recessive and your partner is not a carrier, the risk of an affected child is low. However, if both partners are carriers, or if you have an autosomal dominant condition, PGT-M may be recommended. Discuss your specific situation with a genetic counselor.
Can PGT-A and PGT-M be done together?
Yes, many clinics offer combined PGT (PGT-A+PGT-M) using the same embryo biopsy. This allows screening for both chromosomal abnormalities and a specific genetic mutation.
Does PGT guarantee a healthy baby?
No. PGT reduces the risk of transferring embryos with certain chromosomal or genetic abnormalities, but it cannot guarantee a pregnancy, live birth, or a child free from all health conditions. Some abnormalities may not be detectable, and there is always a small risk of misdiagnosis.
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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