If you are considering IVF and have been told about the types of IVF PGT, you may wonder which test is relevant to you. PGT, or preimplantation genetic testing, examines embryos created through IVF for specific chromosome or genetic concerns before embryo transfer. The right test depends on your medical and genetic history.

Key Takeaways

  • PGT-A checks embryos for missing or extra chromosomes.
  • PGT-M looks for a specific inherited single-gene condition.
  • PGT-SR checks embryos when a parent has certain chromosome structural rearrangements.
  • PGT is performed as part of an IVF process and is not necessary or appropriate for every patient.
  • Your fertility specialist can help determine whether genetic testing is relevant to your circumstances.

What Is PGT in IVF?

Preimplantation genetic testing (PGT) is a laboratory-based genetic test performed on embryos created through in vitro fertilization (IVF). IVF is a fertility treatment in which eggs and sperm are combined in a laboratory to create embryos.

When an embryo develops to the blastocyst stage, typically around day 5 or 6, embryologists can take a small sample of cells from its outer layer for genetic analysis. The embryo is generally cryopreserved while testing is completed, and the results can then help inform decisions about which embryo may be suitable for transfer. PGT does not examine every possible health condition. Instead, the type of PGT determines what the laboratory is specifically looking for.

There are three established clinical categories:

  1. PGT-A – Preimplantation Genetic Testing for Aneuploidy
  2. PGT-M – Preimplantation Genetic Testing for Monogenic Disorders
  3. PGT-SR – Preimplantation Genetic Testing for Structural Rearrangements
Types of IVF PGT Testing

Types of IVF PGT Testing: What Is the Difference?

Although all three tests are grouped under PGT, they are designed for different circumstances.

Type What it checks Usually considered when
PGT-A Number of chromosomes There is concern about chromosome-number abnormalities
PGT-M A specific single-gene condition A known inherited genetic condition may be passed to the child
PGT-SR Structural chromosome rearrangements A parent has a known rearrangement such as a translocation or inversion

Let’s look at each type in more detail.

1. PGT-A: Testing for Chromosome Number Abnormalities

PGT-A stands for Preimplantation Genetic Testing for Aneuploidy.

Aneuploidy means an embryo has an abnormal number of chromosomes. Humans normally have 46 chromosomes arranged in 23 pairs. An embryo may sometimes have an extra or missing chromosome.

PGT-A is designed to identify these chromosome-number abnormalities in embryos before transfer. 

Why might PGT-A be considered?

Your fertility specialist may discuss PGT-A with you depending on factors such as:

  • Maternal age
  • Previous recurrent pregnancy loss
  • Previous unsuccessful IVF treatment
  • Certain previous pregnancy or chromosome findings
  • The number and quality of embryos available
  • Your overall reproductive history

However, PGT-A is not automatically required for everyone undergoing IVF. Its potential value can vary considerably between patients, and professional guidance recognizes that appropriate patient selection remains an important consideration. 

What can PGT-A tell you?

PGT-A can provide information about whether an embryo appears to have the expected chromosome number or shows aneuploidy.

Some embryos may also receive a mosaic result, meaning the tested sample contains a mixture of cells with different chromosome patterns. These results can require careful interpretation rather than being treated as a simple “yes” or “no.” 

Does PGT-A guarantee a healthy pregnancy?

No.

PGT-A can provide valuable information about specific chromosome abnormalities, but it does not test for every genetic or developmental condition. A PGT result also cannot guarantee implantation, pregnancy, or the birth of a healthy baby.

This is why your fertility specialist should interpret PGT results alongside your complete reproductive history.

2. PGT-M: Testing for Single-Gene Conditions

PGT-M stands for Preimplantation Genetic Testing for Monogenic Disorders.

“Monogenic” simply means a condition caused by a change in a single gene.

PGT-M is different from PGT-A because it does not primarily look at whether an embryo has too many or too few chromosomes. Instead, it is designed to test for a specific known genetic condition

Who may consider PGT-M?

PGT-M may be discussed when:

  • You have a known inherited genetic condition.
  • Your partner has a known genetic condition.
  • Both partners are carriers of the same recessive condition.
  • There is a family history suggesting a significant inherited disorder.
  • Genetic testing has identified a specific mutation relevant to reproductive planning.

Examples of single-gene conditions can include disorders such as cystic fibrosis or certain inherited blood disorders, depending on the specific genetic variant involved. 

Why is genetic counselling important?

PGT-M is highly individualized.

Unlike a general chromosome screening panel, testing may need to be designed around the particular genetic condition and family mutation being investigated. This means your fertility team may recommend genetic counselling and additional laboratory preparation before the IVF cycle.

For couples who have experienced the emotional difficulty of an inherited condition within their family, having clear genetic information can also be an important part of treatment planning.

At Almond Blossoms, genetic considerations can be discussed as part of a broader fertility plan rather than treated as an isolated laboratory decision.

3. PGT-SR: Testing for Chromosome Structural Rearrangements

PGT-SR stands for Preimplantation Genetic Testing for Structural Rearrangements.

This type of testing is relevant when a person has a known structural change in their chromosomes.

For example, a person may have a balanced translocation or an inversion. These changes may not necessarily cause health problems in the person carrying them, but they can affect how chromosomes are distributed when eggs or sperm are produced.

As a result, some embryos may inherit an unbalanced chromosome arrangement, which can contribute to implantation failure, miscarriage, or genetic problems. 

When might PGT-SR be discussed?

Your specialist may consider this type of testing if:

  • You or your partner has an identified chromosomal rearrangement.
  • Previous genetic testing showed a translocation or inversion.
  • You have experienced recurrent pregnancy losses and chromosome testing identifies a relevant rearrangement.
  • There is a known genetic reason to assess embryo chromosome structure.

Because PGT-SR is based on a specific chromosome finding, your fertility specialist may recommend parental chromosome testing, known as karyotyping, before determining whether PGT-SR is appropriate.

How Does PGT Work During an IVF Cycle?

PGT cannot be performed independently of embryo creation. It is generally incorporated into an IVF treatment cycle.

The process commonly involves several stages:

1. Ovarian stimulation

Medications are used to encourage the ovaries to develop multiple follicles rather than a single naturally developing egg.

Your response is monitored through ultrasound and, when appropriate, blood tests.

2. Egg retrieval

Once the follicles have developed appropriately, the eggs are collected through a procedure performed under medical supervision.

3. Fertilisation

The retrieved eggs are fertilised in the laboratory.

Depending on your circumstances, this may involve conventional IVF or ICSI (intracytoplasmic sperm injection), where a single sperm is injected directly into an egg.

You can learn more by internally linking the phrase “IVF and ICSI treatment” to Almond Blossoms’ 

4. Embryo development

The fertilised eggs develop in the laboratory.

Embryologists monitor their development until suitable embryos reach the blastocyst stage, generally around day 5 or 6.

5. Embryo biopsy

A small number of cells are removed from the outer layer of the blastocyst.

The sample is sent for genetic analysis while the embryo is cryopreserved.

6. Genetic analysis

The laboratory performs the appropriate test:

  • PGT-A
  • PGT-M
  • PGT-SR

The exact analysis depends on the genetic question being investigated.

7. Results and embryo transfer planning

Once the results are available, your fertility specialist reviews them with you.

A suitable embryo may then be considered for a future frozen embryo transfer, depending on the clinical circumstances.

Because PGT results are not immediately available, embryo freezing is commonly incorporated into treatment involving PGT. Almond Blossoms’ embryo-freezing service explains how embryos can be cryopreserved for later transfer. 

Is PGT-A, PGT-M or PGT-SR Right for You?

There isn’t one “best” PGT test for everyone.

The appropriate approach depends on why genetic testing is being considered in the first place.

For example:

  • If the concern is chromosome number → PGT-A may be considered.
  • If there is a known single-gene condition → PGT-M may be relevant.
  • If a parent has a structural chromosome rearrangement → PGT-SR may be considered.

Your age, ovarian reserve, fertility history, previous pregnancies, family history, genetic test results and number of embryos can all influence treatment planning.

Importantly, AMH (anti-Müllerian hormone) does not tell you which type of PGT you need. AMH is a marker commonly used to help assess ovarian reserve, the approximate remaining egg supply, but it does not diagnose embryo chromosome abnormalities or specific inherited conditions.

A specialist should therefore look at your complete fertility picture rather than relying on a single test result.

What Are the Benefits and Limitations of PGT?

PGT can be an important reproductive tool, but it is not a guarantee of pregnancy or a healthy baby.

Potential benefits

Depending on your circumstances, PGT may:

  • Provide additional genetic information about embryos.
  • Help reduce the likelihood of transferring an embryo affected by a specific tested condition.
  • Help identify embryos with chromosome abnormalities in PGT-A testing.
  • Support reproductive decision-making for couples with known genetic risks.
  • Provide useful information when planning embryo transfer.

Important limitations

PGT also has limitations that you should understand before treatment.

It does not test for every disease.
A PGT test only addresses the genetic or chromosomal issue it was designed to evaluate.

It cannot guarantee pregnancy.
Even an embryo with a favorable PGT result may not implant or result in a live birth.

Results can sometimes be complex.
For example, mosaic PGT-A results may require individualized interpretation

Testing adds cost and time to IVF.
PGT involves additional laboratory procedures, and embryos are generally frozen while results are obtained.

Prenatal testing may still be recommended.
Because PGT is performed using a small embryo biopsy and is not a comprehensive assessment of all possible fetal conditions, prenatal diagnostic testing may still be discussed during pregnancy.

This balanced discussion is particularly important when you are already experiencing the emotional pressure associated with IVF. Understanding what PGT can and cannot tell you can make treatment decisions more manageable.

Frequently Asked Questions (FAQs)

What are the three main types of PGT?

Is PGT included in every IVF cycle?

Does PGT guarantee a healthy baby?

Is PGT painful?

How do I know which PGT test I need?

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