How to Compare PGT-A vs PGT-M vs PGT-SR for Your Situation

What Are PGT-A, PGT-M, and PGT-SR?

Preimplantation genetic testing (PGT) is a set of tests performed on embryos created through IVF before transfer. Each test answers a different question about the embryo’s genetic makeup. Understanding the purpose of each can help you have a more informed conversation with your fertility team.

• PGT-A (aneuploidy screening) checks for the correct number of chromosomes. Embryos with too many or too few chromosomes are called aneuploid and often fail to implant or miscarry.
• PGT-M (monogenic testing) looks for a specific inherited condition caused by a single gene, such as cystic fibrosis or sickle cell disease. It is used when one or both partners carry a known genetic mutation.
• PGT-SR (structural rearrangement testing) detects structural changes in chromosomes, such as inversions or translocations, that can lead to unbalanced chromosomes in embryos.

These tests are not routine for everyone. They are typically offered based on medical history, age, or specific genetic risks. Your clinic will recommend which test, if any, is appropriate for your situation.

At a Glance: Key Differences

• Purpose: PGT-A screens for chromosomal number errors; PGT-M targets a specific gene mutation; PGT-SR checks for chromosomal structural changes.
• Who it’s for: PGT-A is often considered for women of advanced maternal age or those with recurrent miscarriage; PGT-M is for couples with a known genetic condition; PGT-SR is for carriers of balanced structural rearrangements.
• What it requires: All require IVF and embryo biopsy. PGT-M and PGT-SR often require a prior genetic workup of the parents.
• Result interpretation: PGT-A gives a result of euploid (normal), aneuploid (abnormal), or mosaic (mixed). PGT-M and PGT-SR report whether the embryo carries the specific mutation or unbalanced rearrangement.

When Is Each Test Typically Recommended?

PGT-A

PGT-A is often discussed for patients who are older, have had repeated implantation failure, or have experienced recurrent pregnancy loss. It can also be considered for couples who want to reduce the chance of transferring an embryo with a chromosomal abnormality. However, PGT-A does not guarantee a pregnancy or a healthy baby, and its benefit may vary by age and history.

PGT-M

PGT-M is used when one or both partners are known carriers of a single-gene disorder. Before starting, the specific mutation must be identified, and a genetic test must be developed for that family. This process can take time and requires genetic counseling.

PGT-SR

PGT-SR is recommended when a partner carries a balanced structural rearrangement, such as a translocation or inversion. These rearrangements may not affect the carrier’s health but can lead to unbalanced chromosomes in embryos, increasing the risk of miscarriage or birth defects.

How the Testing Process Works

All PGT tests follow a similar process:

1. IVF cycle: You undergo ovarian stimulation and egg retrieval, and embryos are created in the lab.
2. Biopsy: A few cells are removed from each embryo, usually on day 5 or 6 of development.
3. Genetic analysis: The cells are sent to a genetics laboratory for testing. The type of test depends on what you and your clinic have decided.
4. Transfer: Embryos that are considered suitable for transfer are selected based on the test results and other criteria.

The biopsy is a delicate procedure, and not all embryos survive it. Your clinic will explain the risks and benefits in your specific case.

What Do the Results Mean?

Results are not always black and white. For PGT-A, an embryo may be reported as:

• Euploid: normal number of chromosomes.
• Aneuploid: abnormal number.
• Mosaic: a mix of normal and abnormal cells.

For PGT-M and PGT-SR, results indicate whether the embryo carries the specific genetic change tested. However, these tests do not detect all genetic conditions, and they cannot guarantee the health of a child.

Limitations and Considerations

PGT is a screening tool, not a guarantee. It does not eliminate the risk of miscarriage or birth defects, and it does not test for every possible genetic condition. Additionally, the accuracy of the test depends on the laboratory and the number of cells biopsied. There is also a small chance of no result or an inconclusive result.

PGT adds cost and time to an IVF cycle. It also requires a skilled laboratory and experienced team. Discuss with your clinic about the specific technology they use and their success rates with PGT.

Questions to Ask Your Clinic or Genetic Counselor

• Which PGT test do you recommend for my situation, and why?
• What is the process for developing a test for PGT-M or PGT-SR, and how long does it take?
• What are the risks of embryo biopsy?
• How are mosaic embryos handled in your clinic?
• What is the accuracy of the test, and what are the limitations?
• What are the costs involved, and are there any additional fees for genetic counseling?
• How many embryos typically reach the biopsy stage?

Next Steps: Making an Informed Decision

Choosing whether to use PGT is a personal decision. Start by gathering information about your own genetic history and fertility situation. Then, schedule a consultation with a fertility specialist and a genetic counselor. They can help you understand the risks, benefits, and alternatives.

Remember that PGT is not mandatory for everyone. Some couples may choose not to test, and that is a valid option. The goal is to make a decision that aligns with your values and medical needs.

For more general information about PGT in Thailand, see our PGT in Thailand guide. You may also find our guides and FAQ sections helpful.

Frequently asked questions

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

Yes, in some cases, multiple tests can be performed on the same embryo biopsy. For example, if a couple is doing PGT-M for a single-gene disorder, they may also opt for PGT-A to screen for chromosomal abnormalities. However, this depends on the laboratory's capabilities and the embryo's quality. Your clinic can advise whether combined testing is feasible for your situation.

Is PGT-A recommended for all IVF patients?

No, PGT-A is not recommended for everyone. It is often considered for patients of advanced maternal age, those with recurrent implantation failure, or recurrent pregnancy loss. However, its benefit may be limited for younger patients with no known fertility issues. Your doctor will discuss whether PGT-A is appropriate based on your individual circumstances.

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

PGT-M tests for a specific single-gene disorder, such as cystic fibrosis or Huntington's disease, when the parents are known carriers. PGT-SR tests for structural changes in chromosomes, like translocations or inversions, that can cause unbalanced chromosomes in embryos. Both require prior genetic testing of the parents to develop the test.

How long does PGT testing take?

The time can vary. After embryo biopsy, results may take anywhere from a few days to a few weeks, depending on the type of test and the laboratory. PGT-M and PGT-SR often require additional time for test development before the IVF cycle even starts. Your clinic will provide a timeline based on your specific plan.

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.