PGT-A vs. PGT-M: What Is the Difference?

PGT-A vs. PGT-M can be confusing when you are exploring IVF and embryo genetic testing. The key difference is simple: PGT-A checks embryos for missing or extra chromosomes, while PGT-M looks for a specific inherited single-gene condition. Both require IVF and embryo biopsy, but they are used for different genetic concerns. 

If you are considering fertility treatment in Dubai, understanding this distinction can help you have a more informed conversation with your fertility specialist.

PGT-A focuses on chromosome number. PGT-M focuses on a known genetic condition caused by a change in a single gene. Neither test guarantees pregnancy or a healthy baby.

PGT-A vs. PGT-M: What Is the Main Difference?

Although both are forms of preimplantation genetic testing (PGT), they answer different questions about an embryo.

Feature	PGT-A	PGT-M
Full name	Preimplantation Genetic Testing for Aneuploidy	Preimplantation Genetic Testing for Monogenic Disorders
Main purpose	Screens chromosome number	Tests for a specific single-gene condition
Looks for	Missing or extra chromosomes	A known genetic variant/mutation
Usually considered when	Chromosomal risk is a concern	There is a known inherited genetic risk
Requires IVF?	Yes	Yes
Requires embryo biopsy?	Yes	Yes
Tests every genetic disease?	No	No
Guarantees pregnancy?	No	No

Aneuploidy means an embryo has an abnormal number of chromosomes. Humans typically have 46 chromosomes arranged in 23 pairs. PGT-A assesses whether the embryo has the expected chromosome number.

A monogenic disorder, on the other hand, is a condition caused by a change in one particular gene. PGT-M is designed to look for a specific known genetic condition.

So, in very simple terms:

PGT-A = “Does this embryo have the expected number of chromosomes?”

PGT-M = “Does this embryo carry the specific genetic condition we are concerned about?”

What Is PGT-A and Who May Consider It?

PGT-A (Preimplantation Genetic Testing for Aneuploidy) is an embryo screening test used during IVF.

During the process, embryos are developed in the laboratory. Once an embryo reaches the blastocyst stage, the stage when it has developed into a more advanced group of cells, a small sample of cells can be removed for genetic analysis.

The laboratory then examines the chromosomes in the sample.

What can PGT-A identify?

PGT-A can identify embryos with chromosome-number abnormalities, including embryos with:

• An extra chromosome
• A missing chromosome
• Certain chromosome-number abnormalities that may affect implantation or pregnancy development

For example, an additional copy of chromosome 21 is associated with Down syndrome.

However, PGT-A is not a complete genetic health check. It does not examine every gene or rule out every possible medical condition.

Why might your fertility specialist discuss PGT-A?

Your specialist may discuss PGT-A based on factors such as your age, reproductive history, number of embryos available, previous IVF outcomes, and overall treatment goals.

Importantly, PGT-A is not automatically appropriate for everyone undergoing IVF. Current evidence does not support treating it as a routine requirement for every IVF patient. The potential benefits and limitations should be assessed individually.

This is particularly important if you are likely to have only a small number of embryos. Testing can provide additional information, but the process may also result in fewer embryos being available for transfer depending on the results.

What Is PGT-M and When Is It Used?

PGT-M (Preimplantation Genetic Testing for Monogenic Disorders) is different from PGT-A because it focuses on a specific inherited condition caused by a change in a single gene.

It may be considered when there is a known genetic risk within your family or when testing has identified a particular genetic variant in one or both intended parents.

Examples of conditions that may be considered for PGT-M include certain forms of:

• Cystic fibrosis
• Sickle cell disease
• Huntington’s disease
• Some inherited blood disorders
• Other known single-gene disorders

The important point is that PGT-M is targeted. It is not a general genetic test for every possible inherited condition.

How does PGT-M work?

PGT-M generally involves several stages:

1. Identify the genetic condition or variant being tested.
2. Assess the genetic information of the intended parents and, when needed, other family members.
3. Develop and validate a testing strategy specific to the genetic condition.
4. Create embryos through IVF.
5. Biopsy suitable embryos and send the samples for genetic analysis.
6. Review the results with your fertility and genetics team.
7. Consider an appropriate embryo for transfer based on the complete clinical picture.

Because PGT-M is customized to a particular genetic condition, preparation can be more involved than patients sometimes expect.

Your fertility specialist and genetic counsellor can explain what preparation is needed in your specific circumstances.

PGT-A vs. PGT-M: Which One Is Right for You?

There is no universal answer to whether PGT-A or PGT-M is “better.”

They are designed for different purposes.

PGT-A may be discussed when:

• Chromosome-number abnormalities are a particular concern
• You are undergoing IVF and have embryos suitable for testing
• Your reproductive history or age makes chromosome-related questions clinically relevant
• Your fertility specialist believes chromosome screening could provide useful information for embryo selection

PGT-M may be discussed when:

• You or your partner have a known disease-causing genetic variant
• Both partners are carriers of a particular recessive condition
• There is a known inherited condition in your family
• Genetic testing identifies a specific reproductive risk
• You want to reduce the possibility of passing a known single-gene condition to a child

Your specialist may also discuss PGT-SR, another form of PGT used for certain structural chromosome rearrangements, such as translocations.

Can PGT-A and PGT-M be done together?

In some circumstances, yes.

If a couple has a known single-gene condition and also has a reason to consider chromosome screening, a laboratory may be able to perform PGT-M and PGT-A on embryos within the same IVF treatment.

Whether this is appropriate depends on the specific genetic condition, laboratory testing strategy, embryo availability and clinical circumstances.

This is one reason why discussing your family history and previous genetic testing with your fertility specialist before starting treatment can be valuable.

How Are PGT-A and PGT-M Performed During IVF?

Both tests are connected to in vitro fertilisation (IVF), which means eggs are collected and fertilised with sperm in a laboratory rather than through unassisted conception.

In some cases, ICSI (intracytoplasmic sperm injection) is used. ICSI is a laboratory fertilisation technique in which a single sperm is injected directly into an egg.

A simplified process looks like this:

1. Ovarian stimulation

Medications are used to stimulate the ovaries so that multiple eggs may mature during the treatment cycle.

2. Egg retrieval

The mature eggs are collected during a procedure performed by the fertility team.

3. Fertilisation

The eggs are fertilised with sperm using IVF and, where appropriate, ICSI.

4. Embryo development

The resulting embryos are cultured in the laboratory and monitored as they develop.

5. Embryo biopsy

When appropriate embryos reach the blastocyst stage, a small number of cells are collected for genetic testing.

6. Genetic analysis

The biopsy sample is analyzed according to the test selected:

• PGT-A: chromosome-number screening
• PGT-M: targeted testing for a specific single-gene condition

7. Embryo transfer planning

Embryos are generally frozen while testing and laboratory processes are completed. The fertility team then discusses which embryo may be appropriate for transfer.

Importantly, PGT does not repair an embryo or change its chromosomes or genes. It provides additional genetic information that may help inform embryo selection. 

Does PGT Guarantee a Healthy Baby or Successful IVF?

No. This is one of the most important things to understand before choosing embryo genetic testing.

PGT can provide valuable information, but it cannot guarantee implantation, pregnancy, live birth, or the absence of every genetic or medical condition.

There are several reasons.

First, embryo biopsy examines only a small number of cells. The result may not represent every cell in the embryo.

Second, PGT-A is a screening test, rather than a guarantee that an embryo is completely free from genetic abnormalities.

Third, PGT-M is designed around a specific known genetic condition. A result showing that an embryo is unaffected by that condition does not mean the embryo has no other health risks.

For these reasons, professional guidance recommends appropriate prenatal screening or diagnostic testing during pregnancy even after PGT. ACOG notes that confirmation of PGT-M results through prenatal diagnostic testing such as chorionic villus sampling or amniocentesis should be offered.

What happens if the result is “mosaic”?

You may also hear the term mosaic embryo.

Mosaicism means the tested sample contains a mixture of cells with different chromosome findings. These results can be more complicated to interpret than a straightforward result.

The decision about whether a mosaic embryo may be suitable for transfer requires individualized assessment by your fertility and genetics team.

This can understandably feel emotionally difficult. Having a fertility specialist explain the result and access to appropriate psychological support when needed can help you process the information before making a decision.