PGT-A vs PGT-M vs PGT-SR: Understanding Genetic Testing Options in Thailand

If you are exploring IVF in Thailand, you may come across terms like PGT-A, PGT-M, and PGT-SR. These are different types of preimplantation genetic testing (PGT) that can be performed on embryos before transfer. Each test serves a distinct purpose, and understanding the differences can help you have more informed conversations with your fertility team. This guide explains what each test looks for, when it might be used, and what to consider when comparing options.

What Is PGT?

Preimplantation genetic testing (PGT) is a procedure that involves taking a small sample of cells from an embryo created through IVF. The sample is then analyzed in a laboratory to look for specific genetic information. PGT is not a routine step for every IVF cycle; it is typically recommended based on individual medical history, age, or genetic risk factors.

There are three main types of PGT:

• PGT-A (aneuploidy screening)
• PGT-M (monogenic disorders)
• PGT-SR (structural rearrangements)

Each type answers a different question about the embryo.

PGT-A: Screening for Chromosomal Number

PGT-A, previously known as preimplantation genetic screening (PGS), checks embryos for an abnormal number of chromosomes, a condition called aneuploidy. Humans typically have 46 chromosomes in each cell. Having an extra or missing chromosome can lead to implantation failure, miscarriage, or conditions such as Down syndrome.

PGT-A is often considered for:

• Women of advanced maternal age
• Couples with a history of recurrent miscarriage
• Couples with repeated implantation failure
• Couples where the male partner has severe sperm abnormalities

It is important to note that PGT-A does not test for every genetic condition. It only screens for chromosomal number abnormalities, not for specific gene mutations.

PGT-M: Testing for Single-Gene Disorders

PGT-M is used when there is a known risk of passing on a specific inherited condition caused by a mutation in a single gene. Examples include cystic fibrosis, sickle cell anemia, Tay-Sachs disease, and Huntington’s disease. This test identifies embryos that carry the gene mutation, allowing the transfer of embryos without the disorder.

PGT-M is typically recommended when:

• One or both partners are carriers of a known genetic disorder
• There is a family history of a specific single-gene condition
• A previous child has been affected by such a condition

Because PGT-M requires knowing the exact genetic mutation, it often involves a preparatory workup to develop a customized test for each couple.

PGT-SR: Detecting Structural Chromosomal Changes

PGT-SR is designed for couples where one partner carries a structural rearrangement of chromosomes, such as a translocation or inversion. These rearrangements may not cause health problems in the carrier, but they can lead to embryos with unbalanced chromosomal material, increasing the risk of miscarriage or birth defects.

PGT-SR is considered when:

• One partner has a known chromosomal rearrangement
• There is a history of recurrent miscarriages linked to chromosomal abnormalities
• A previous pregnancy had an unbalanced chromosomal arrangement

This test helps identify embryos with a normal or balanced chromosomal structure, which may have a higher chance of leading to a healthy pregnancy.

Key Differences at a Glance

Test	Purpose	Typical Indications
PGT-A	Screens for abnormal chromosome number	Advanced maternal age, recurrent miscarriage, repeated implantation failure
PGT-M	Detects specific single-gene mutations	Known carrier status or family history of a genetic disorder
PGT-SR	Identifies structural chromosomal rearrangements	Known translocation or inversion in a partner, recurrent miscarriage

How Are the Tests Performed?

All PGT types follow a similar process: after IVF fertilization, embryos are cultured for several days, and a biopsy is taken from the trophectoderm (the cells that will become the placenta). The biopsy is then sent to a genetics laboratory for analysis. The embryo is frozen while waiting for results.

The main differences lie in the laboratory techniques used:

• PGT-A typically uses next-generation sequencing (NGS) to count chromosomes.
• PGT-M uses polymerase chain reaction (PCR) or other methods to detect specific gene mutations.
• PGT-SR may use NGS or other techniques to analyze chromosomal structure.

Your clinic will advise on the specific technology they use and the timeline for results.

Which Test Should You Choose?

The choice between PGT-A, PGT-M, and PGT-SR depends on your medical history and genetic background. There is no one-size-fits-all answer. Here are some steps to help you decide:

1. Consult with a genetic counselor to review your family history and any known genetic risks.
2. Undergo carrier screening if you have not already, to identify potential recessive conditions.
3. Discuss your IVF history with your fertility specialist, including any previous miscarriages or implantation failures.
4. Ask your clinic which PGT types they offer and whether they have experience with your specific situation.

Remember, PGT is not a guarantee of a successful pregnancy or a healthy baby. It is a screening tool that can provide information to help guide embryo selection.

Questions to Ask Your Clinic

When comparing PGT options in Thailand, consider asking:

• Which PGT tests do you offer, and what is the laboratory accreditation?
• How many embryos typically survive the biopsy and freezing process?
• What is the turnaround time for results?
• Are there additional costs for genetic counseling or carrier screening?
• How do you handle inconclusive results or mosaicism?

Next Steps

If you are considering PGT in Thailand, start by gathering your medical records and any prior genetic testing results. Then, schedule consultations with fertility clinics that offer PGT services. Use this guide to ask informed questions and understand the purpose of each test.

For more information, explore our PGT in Thailand overview, read our patient guides, or check our FAQ for common questions.

Frequently asked questions

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

PGT-A screens embryos for an abnormal number of chromosomes (aneuploidy), while PGT-M tests for specific single-gene disorders when there is a known genetic risk. PGT-A is often used for age-related or unexplained fertility issues, whereas PGT-M is used for couples who carry a specific gene mutation.

Is PGT-SR the same as PGT-A?

No. PGT-SR is used when one partner has a structural chromosomal rearrangement, such as a translocation. It looks for unbalanced chromosomal material. PGT-A only checks the number of chromosomes, not their structure.

Can PGT-A detect all genetic disorders?

No. PGT-A only screens for chromosomal number abnormalities. It does not detect single-gene disorders or structural rearrangements. For those, PGT-M or PGT-SR would be needed.

Do I need PGT if I am young and healthy?

PGT is not necessary for everyone. It is typically recommended based on specific medical indications, such as advanced maternal age, recurrent miscarriage, or known genetic risks. Your fertility specialist can help you decide if PGT is appropriate for you.

How long does PGT testing take in Thailand?

The timeline can vary depending on the clinic and the type of test. Typically, results may take several days to a few weeks. Your clinic will provide a specific timeline based on their laboratory processes.

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.