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What Are the Differences Between PGT-A, PGT-M, and PGT-SR, and Which Cases Are They Suitable For?

Infertility treatment in 2025 is advancing towards more personalized care, utilizing Preimplantation Genetic Testing (PGT) for highly accurate genetic screening of embryos.

PGT (Preimplantation Genetic Testing) is a technique for analyzing the genetics of embryos prior to their transfer into the uterine cavity during the IVF/ICSI process. This enables the selection of chromosomally normal or the “”healthiest”” embryos for pregnancy.

The genetic analysis of embryos allows physicians to screen for chromosomal or genetic abnormalities, which are significant causes of miscarriage, implantation failure, or abnormal fetal development. This is particularly beneficial for women over the age of 35 or couples with a history of recurrent unexplained miscarriages.

PGT-A, PGT-M, and PGT-SR: Selecting the appropriate test based on your risk profile

STEP 01 — PGT-A | Assessing Chromosome Quantity

Evaluates whether the embryo possesses a complete set of chromosomes or exhibits numerical abnormalities (extra or missing chromosomes). This test is suitable for assessing the risk of numerical chromosomal abnormalities.

STEP 02 — PGT-M | Identifying Disease-Causing Genes

Detects specific single-gene mutations with known etiologies. This test is suitable for couples who are carriers or have an identified risk of specific genetic disorders.

STEP 03 — PGT-SR | Analyzing Chromosome Structure

Detects structural chromosomal abnormalities, such as translocations or inversions. This test is suitable for couples who have been diagnosed with structural chromosomal abnormalities.

STEP 04 — Tailoring the Approach to Individual Risk Profiles

There is no universal approach to PGT. The physician will carefully evaluate factors such as age, pregnancy history, family history, and the couple’s genetic test results to determine the most appropriate testing strategy.

Types of Preimplantation Genetic Testing (PGT)

Preimplantation Genetic Testing (PGT) can be divided into three main types depending on the purpose of the test and the genetic issues to be identified. Each type has a different goal to increase the chances of pregnancy and reduce the risk of miscarriage or genetic diseases in children, as follows:

PGT-A: Preimplantation Genetic Testing for Aneuploidy

PGT-A is a screening test for abnormalities in the number of chromosomes in the embryo across all 23 pairs to determine if there are missing (Monosomy) or extra (Trisomy) chromosomes. These abnormalities are major causes of Down syndrome (Trisomy 21), miscarriage, or the embryo’s inability to implant and develop normally.

Benefits of PGT-A

Helps select embryos without numerical chromosomal abnormalities (Euploid).
Reduces the risk of early miscarriage.
Increases the chances of successful embryo implantation and pregnancy.
Reduces the risk of chromosomal missing/extra conditions that may affect the baby’s health.

Who is PGT-A suitable for?

Women aged 35 and older.
Couples with a history of recurrent unexplained miscarriages.
Couples who have experienced multiple failed IVF/ICSI cycles.
Individuals who wish to reduce the risk of having a baby with numerical chromosomal abnormalities.

PGT-M: Preimplantation Genetic Testing for Monogenic/Single Gene Disorder

PGT-M is a specific test at the gene level to detect mutations or abnormalities in a single gene known to cause genetic diseases inherited from parents, such as Thalassemia, Cystic Fibrosis, or Spinal Muscular Atrophy (SMA).

Benefits of PGT-M

Prevents the transmission of genetic diseases from generation to generation.
Reduces the chances of a pregnancy with a baby having severe abnormalities.
Boosts confidence for families with a history of genetic diseases.

Who is PGT-M suitable for?

Couples who are known carriers of severe single-gene disorders.
Couples who have previously had a child with a single-gene disorder.
Individuals with a clear family history of genetic diseases.

PGT-SR: Preimplantation Genetic Testing for Structural Rearrangements

PGT-SR is a specialized test designed for couples where one partner is a carrier of a chromosomal rearrangement (Balanced Translocation or Inversion), which is a major cause of recurrent miscarriages, failed pregnancies, or the risk of a baby being born with congenital abnormalities.

Balanced Translocation refers to the exchange of segments between two chromosomes without any loss or gain of genetic material. Carriers usually do not exhibit any health abnormalities. However, during the formation of reproductive cells (eggs or sperm), faulty chromosome rearrangement can occur, leading to embryos with missing or extra chromosomal segments (Unbalanced Translocation). This is a primary cause of recurrent miscarriages, embryo growth arrest, or severe birth defects.

Benefits of PGT-SR

Helps separate embryos with missing or extra chromosomal segments from those with normal structures or a Balanced Translocation like the parents.
Reduces the risk of recurrent miscarriages and failed pregnancies due to chromosomal abnormalities.
Allows physicians to select only embryos without chromosomal abnormalities (Euploid / Balanced) to increase the chances of a successful pregnancy.
Increases confidence for couples with a history of recurrent miscarriages or a family history of chromosomal abnormalities.
Increases the chances of having a healthy baby free from genetic problems caused by structural chromosomal abnormalities.

Who is PGT-SR suitable for?

Couples with a history of two or more recurrent miscarriages without a clear cause.
Couples who have been diagnosed as carriers of a Balanced Translocation or Inversion.
Individuals who have previously had a child or fetus with chromosomal abnormalities, such as missing or extra chromosomal segments.
Individuals who wish to reduce the risk of transmitting structural chromosomal abnormalities to the next generation.

Summary of the differences between PGT-A, PGT-M, and PGT-SR

PGT-A tests for abnormalities in the “number” of chromosomes, such as missing or extra chromosomes (Aneuploidy).
PGT-M is a genetic test at the “single gene” level (Single Gene Disorder) to detect gene mutations that cause genetic diseases such as Thalassemia, Spinal Muscular Atrophy (SMA), or Cystic Fibrosis. It is suitable for couples who are carriers of genetic diseases.
PGT-SR tests for abnormalities in the “structure” of chromosomes to help select embryos without chromosomal abnormalities resulting from a parent being a carrier of a chromosomal rearrangement (Translocation or Inversion). It is an approach to help reduce the risk of miscarriage and increase the chances of a successful pregnancy.

การตรวจพันธุกรรมตัวอ่อน (PGT-A, PGT-M, PGT-SR)

Why is PGT Important for Infertility Treatment?

Benefits of PGT: Reducing the Risk of Miscarriage and Genetic Abnormalities
PGT allows physicians to identify and select embryos with a low risk of chromosomal or genetic abnormalities, leading to significant benefits:

Increases pregnancy success rates, especially in individuals with recurrent miscarriages or advanced maternal age.
Reduces the miscarriage rate, as chromosomally abnormal embryos are the primary cause of first-trimester miscarriages.
Lowers the risk of congenital anomalies in the baby, such as Down Syndrome or other genetic disorders.
Decreases the need for multiple embryo transfers, thereby reducing the risk of multiple pregnancies.

Factors Physicians Consider Before Selecting the PGT Type

Choosing the appropriate PGT type requires evaluating various medical factors and the couple’s history, including:

Maternal age, particularly for women aged 35 and above, as the risk of embryos having extra or missing chromosomes (aneuploidy) increases significantly.
Family history. If there is a clear history of inherited genetic diseases, such as Thalassemia or Muscular Dystrophy, the physician will consider genetic screening to check for gene abnormalities.
History of miscarriages. If there is a history of two or more recurrent miscarriages, especially in the first trimester, which are mostly caused by embryonic chromosomal abnormalities.
History of repeated IVF failures. Even after screening and transferring good-quality embryos, if implantation fails, the physician will recommend further screening before starting a new cycle.

Recommendations for Embryonic Chromosomal and Genetic Screening

Consult a Genetic Counselor or Doctor to assess the necessity and select the appropriate type of PGT-A, PGT-M, or PGT-SR.
– Prepare your body before egg and sperm retrieval by getting adequate rest, eating a nutritious diet, and avoiding stress.
Understand that PGT is a ‘supplementary process’ for embryo selection, not a direct genetic modification.
Keep in mind that test results may have limitations, and you should follow up closely with your physician.
Plan your treatment and embryo transfer with a multidisciplinary team to increase the chances of a successful pregnancy.

Embryonic chromosomal and genetic screening (PGT-A, PGT-M, PGT-SR) enables individuals experiencing infertility to select healthy embryos, reduce the risk of miscarriage, and increase the likelihood of a successful pregnancy with greater confidence.

คำถามที่พบบ่อย

Is PGT painful and how long does it take?

PGT does not directly cause pain to the patient because the testing process involves collecting a few cells from the embryo in the laboratory after IVF or ICSI, which are then analyzed. Therefore, it does not directly affect your body. The testing process typically takes about 1–2 weeks before the results are known, depending on the type of test (PGT-A, PGT-M, or PGT-SR) and the laboratory procedures used.

Does PGT really increase the chances of a successful pregnancy?

Yes, it does. PGT-A, PGT-M, and PGT-SR are medically supported to significantly increase the success rate of pregnancy. This is because they help select only embryos without chromosomal abnormalities (Euploid) to reduce the chances of miscarriage, reduce implantation failure, and reduce the risk of genetic abnormalities in the baby, especially in women over 35 years old or those with a history of recurrent miscarriage.

What are the limitations or risks of PGT that should be known before making a decision?

Although PGT helps reduce the risk of abnormal embryos and increases the chances of a successful pregnancy, there are still limitations to be aware of. It cannot guarantee a 100% pregnancy outcome, as other factors are involved, such as uterine age and overall health. It also cannot detect very small abnormalities (Microdeletion / Microduplication) and must be done in conjunction with the IVF/ICSI process.

Frequently Asked Questions

What Are the Differences Between PGT-A, PGT-M, and PGT-SR, and Which Cases Are They Suitable For?