PGT-A vs PGT-M: Understanding the Difference

If you are exploring IVF with genetic testing, you may have come across the terms PGT-A and PGT-M. Both are types of preimplantation genetic testing (PGT) performed on embryos before transfer, but they serve different purposes. In short, PGT-A checks embryos for an abnormal number of chromosomes (aneuploidy), while PGT-M looks for a specific single-gene disorder that runs in the family. This guide explains the difference in plain language, helping you understand which test may be relevant based on your medical history and what to discuss with your fertility team.

At a glance: PGT-A vs PGT-M

• PGT-A (Preimplantation Genetic Testing for Aneuploidy) screens embryos for chromosomal abnormalities, such as having an extra or missing chromosome.
• PGT-M (Preimplantation Genetic Testing for Monogenic disorders) tests embryos for a specific inherited condition caused by a mutation in a single gene, such as cystic fibrosis or Huntington’s disease.
• Both tests require IVF and biopsy of a few cells from the embryo.
• Neither test guarantees a pregnancy or a healthy baby; they are screening tools to help select embryos for transfer.

What is PGT-A?

PGT-A is a screening test that looks at the number of chromosomes in an embryo. Humans typically have 46 chromosomes (23 pairs). An embryo with an abnormal number of chromosomes is called aneuploid. Most aneuploid embryos fail to implant or result in miscarriage, and some can lead to conditions like Down syndrome (trisomy 21).

PGT-A is often considered for patients who are of advanced maternal age, have experienced recurrent pregnancy loss, or have had multiple failed IVF cycles. However, it is not a routine requirement for everyone. The test can help identify embryos that are more likely to implant, but it does not guarantee success.

What PGT-A can and cannot tell you

• Can tell: Whether the embryo has the expected number of chromosomes (euploid) or an abnormal number (aneuploid).
• Cannot tell: Whether the embryo carries a specific gene mutation, nor can it predict the child’s future health, intelligence, or physical traits.

What is PGT-M?

PGT-M is a targeted test for a specific monogenic disorder—a condition caused by a mutation in a single gene. It is used when one or both parents are known carriers of a genetic condition, or when there is a family history of a specific disorder. The test identifies embryos that do not carry the mutation, allowing transfer of unaffected embryos.

PGT-M requires prior genetic testing of the parents to identify the exact mutation. The test is then customized for each family. It is not a general screening test; it only looks for the specific condition it was designed to detect.

Examples of conditions PGT-M can test for

• Cystic fibrosis
• Tay-Sachs disease
• Sickle cell anemia
• Huntington’s disease
• Thalassemia

This list is not exhaustive. The availability of PGT-M for a particular condition depends on the genetic cause and the laboratory’s capabilities.

Key differences between PGT-A and PGT-M

Aspect	PGT-A	PGT-M
Purpose	Screens for chromosomal abnormalities (aneuploidy)	Tests for a specific single-gene disorder
Who may consider it	Patients with advanced maternal age, recurrent miscarriage, or repeated implantation failure	Couples who are carriers of a genetic condition or have a family history of a specific disorder
Requires prior genetic testing of parents?	No	Yes, to identify the specific mutation
Result	Embryo classified as euploid (normal chromosome number) or aneuploid (abnormal)	Embryo classified as affected or unaffected for the specific condition
Scope	Broad screening of all chromosomes	Targeted to one gene

Which test is right for you?

The choice between PGT-A and PGT-M depends on your medical history and genetic background. Some patients may benefit from both tests simultaneously, a process sometimes called PGT-A + PGT-M. However, this is not necessary for everyone.

Your fertility specialist and a genetic counselor can help you understand your risks and the potential benefits of each test. They will review your history, any previous genetic testing, and your family background to make a recommendation.

Questions to ask your clinic

• Based on my age and history, is PGT-A recommended for me?
• Do I need genetic carrier screening before considering PGT-M?
• What is the biopsy procedure and how many cells are removed?
• How long does testing take, and will embryos be frozen while waiting for results?
• What are the limitations of these tests?

Limitations and considerations

It is important to understand that PGT is not a guarantee of a successful pregnancy or a healthy baby. Embryos can be mosaic, meaning they have a mix of normal and abnormal cells, and results may not always be clear-cut. Additionally, PGT does not detect all genetic disorders or birth defects.

PGT-A and PGT-M are optional tests. Some patients choose not to have them, and that is a valid decision. Your medical team can provide guidance, but the final choice is yours.

Next steps

If you are considering PGT in Thailand, start by consulting with a fertility clinic that offers genetic testing services. Ask about their laboratory protocols, the experience of their embryologists, and the genetic counseling support they provide. You may also want to discuss the legal and ethical aspects of PGT in Thailand, as regulations can vary.

For more information, explore our PGT in Thailand guide, read other educational guides, or check our FAQ section for common questions.

Frequently asked questions

Can PGT-A and PGT-M be done at the same time?

Yes, it is possible to perform both PGT-A and PGT-M on the same embryo biopsy. This is often done when a couple is at risk for a single-gene disorder and also wants to screen for chromosomal abnormalities. However, not all embryos may be suitable for both tests, and the decision should be made with your fertility team.

Is PGT-A necessary for everyone doing IVF?

No, PGT-A is not necessary for everyone. It is often recommended for women of advanced maternal age, couples with recurrent pregnancy loss, or those with repeated implantation failure. However, for younger women with no known fertility issues, the benefit may be less clear. Discuss your specific situation with your doctor.

Does PGT-M require prior genetic testing of the parents?

Yes, PGT-M requires that the specific genetic mutation in the parents be identified first. This is usually done through carrier screening or diagnostic genetic testing. Without knowing the exact mutation, the test cannot be designed.

What is the difference between PGT-A and PGT-SR?

PGT-SR (Preimplantation Genetic Testing for Structural Rearrangements) is used when one parent has a chromosomal rearrangement, such as a translocation, which can lead to embryos with unbalanced chromosomes. PGT-A screens for aneuploidy in general, while PGT-SR is specifically for structural abnormalities. Some labs may combine these tests.

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.