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1. PGT-A (Preimplantation Genetic Testing for Aneuploidy) checks an embryo's chromosomes. Chromosomes carry genetic information, and most people have 46 of them, arranged in 23 pairs. An embryo with an extra or missing chromosome has a condition called aneuploidy. PGT-A was previously known as PGS (Preimplantation Genetic Screening).

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At Siam Fertility Clinic - Bangkok, Thailand, PGT-A looks at:

• Chromosome number: whether an embryo has an extra or missing whole chromosome.

• Copy-number variations (CNVs): whether a section of a chromosome is missing or duplicated.

• Ploidy: whether the embryo has the expected number of complete chromosome sets.

 

How can PGT-A support your treatment?​

An embryo with an extra or missing chromosome is less likely to implant or may result in early pregnancy loss. PGT-A helps identify embryos with the expected number of chromosomes, so you and your doctor can decide which embryo to transfer first. For some patients, this may:

• Help prioritize embryos with the typical number of chromosomes (euploid) for transfer.

• Reduce the chance of transferring an embryo with a chromosome difference.

• Provide clearer information after previous miscarriage or unsuccessful treatment.

    ** PGT-A cannot guarantee implantation or pregnancy, and results vary from person to person.

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​Who might consider PGT-A?

PGT-A gives you information about your embryos' chromosomes to support your treatment plan. Your doctor may discuss it with you if:

       • You are 35 or older.

       • You have experienced recurrent miscarriage.

       • You have had unsuccessful IVF treatment.

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2. PGT-SR (Preimplantation Genetic Testing for Structural Rearrangements) assesses an embryo when a parent carries a known structural change in their chromosomes, such as a translocation or inversion. A parent with a balanced rearrangement is often healthy, but the change can affect the chromosomes passed on to an embryo.

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​PGT-SR is different from PGT-A. PGT-A looks at the number of chromosomes, while PGT-SR looks at the structure.

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How can PGT-SR support your treatment?
PGT-SR helps identify embryos that may have inherited an unbalanced chromosome change from a parent. This information can help you and your doctor decide which embryo to transfer first. PGT-SR cannot guarantee implantation or pregnancy, and results vary from person to person.

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Who might consider PGT-SR?
Your doctor may discuss PGT-SR with you if you or your partner:

• Have been diagnosed with a structural chromosome rearrangement (for example, a translocation).

• Have had recurrent miscarriage linked to a parent's chromosome rearrangement.

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​​​​​3. PGT-M (Preimplantation Genetic Testing for Monogenic Disorders) tests an embryo for a specific inherited condition caused by a change in a single gene, such as thalassemia. Genes are segments of DNA that carry instructions for how the body develops and functions. We each inherit two copies of most genes, one from each parent, and a change in one or both copies can be passed on to the next generation.

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PGT-M is different from PGT-A. PGT-A looks at the number of chromosomes, while PGT-M looks for one known gene change that has already been identified in a family.

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How can PGT-M support your treatment?
PGT-M helps identify embryos that have not inherited the specific gene change being tested for, so you and your doctor can decide which embryo to transfer first. For families at known risk, this may help reduce the chance of passing on that particular condition.

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The test is planned around your family's specific gene change. It is not a general screen for every genetic disease, and it does not test for conditions influenced by many genes and lifestyle, such as diabetes or heart disease. PGT-M cannot guarantee implantation or pregnancy, and results vary from person to person.

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Who might consider PGT-M?
Your doctor may discuss PGT-M with you if:

• You or your partner carry a known gene change linked to an inherited condition.

• You already have a child with a single-gene condition.

• There is a known single-gene condition in your family.

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Examples of single-gene conditions that may be considered for PGT-M:

• Thalassemia including beta-thalassemia and HbE/beta-thalassemia

• Hemophilia A and B

• Duchenne muscular dystrophy

• Spinal muscular atrophy (SMA)

• Autosomal dominant polycystic kidney disease (ADPKD)

Whether a test can be set up for your condition needs to be confirmed with our genetics team.

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Not sure which test applies to you?
PGT is not necessary for everyone. Speak with our team about your medical and family history, and we will help you decide whether PGT-A, PGT-SR or PGT-M fits your treatment plan. Book a consultation.

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