Understanding PGT-P: Polygenic Risk Testing in IVF

PGT-P (preimplantation genetic testing for polygenic disorders) is a newer type of genetic screening that estimates the likelihood of an embryo developing certain common conditions influenced by multiple genes, such as type 2 diabetes, heart disease, or autoimmune disorders. Unlike PGT-A (aneuploidy screening) or PGT-M (single-gene disorder testing), PGT-P does not look for a specific mutation but rather calculates a polygenic risk score based on many genetic variants.

In Thailand, PGT-P is available at some fertility centers, but it is not universally recommended. It is considered an emerging technology with ongoing debate about its clinical utility. This guide explains what PGT-P is, how it differs from other PGT tests, when it might be considered, and important limitations to discuss with your doctor.

At a Glance: Key Points About PGT-P

• PGT-P estimates risk for common polygenic conditions, not single-gene disorders.
• It is an optional, emerging test—not a standard part of IVF.
• Results are probabilistic, not diagnostic.
• Availability and policies vary by clinic in Thailand.
• Discuss with a genetic counselor to understand benefits and limitations.

What Is PGT-P?

PGT-P stands for preimplantation genetic testing for polygenic disorders. It is a technique that analyzes embryos created through IVF to estimate their genetic risk for conditions that are influenced by many genes and environmental factors. These conditions include type 2 diabetes, coronary artery disease, certain cancers, and autoimmune diseases.

The test calculates a polygenic risk score (PRS) by looking at thousands of small genetic variations across the genome. Each variation contributes a small amount to the overall risk. The score is compared to a reference population to estimate whether an embryo has a higher or lower relative risk for a particular condition.

It is important to understand that PGT-P does not diagnose a disease. It only provides a statistical estimate of risk. A high-risk score does not mean the child will definitely develop the condition, and a low-risk score does not guarantee protection.

How PGT-P Differs from PGT-A and PGT-M

To understand PGT-P, it helps to know the other common types of PGT:

• PGT-A (aneuploidy screening): Checks for the correct number of chromosomes. It identifies embryos with extra or missing chromosomes, which often cause implantation failure or miscarriage.
• PGT-M (monogenic disorders): Tests for a specific single-gene mutation, such as cystic fibrosis or Huntington’s disease, when one or both parents carry the mutation.
• PGT-SR (structural rearrangements): Detects chromosomal structural changes like translocations or inversions.

PGT-P is different because it does not look for a specific mutation or chromosomal abnormality. Instead, it assesses the combined effect of many genetic variants to estimate risk for common, complex diseases.

When Is PGT-P Recommended?

PGT-P is not a routine test. It may be considered in specific situations, such as:

• When a couple has a strong family history of a polygenic condition, such as early-onset heart disease or type 2 diabetes.
• When patients are already undergoing IVF with PGT-A and want additional risk information.
• When patients are interested in reducing the likelihood of passing on polygenic risk to their children.

However, professional guidelines vary. Many reproductive medicine societies do not yet endorse PGT-P for routine use due to limited evidence and ethical concerns. It is essential to discuss with your fertility specialist and a genetic counselor whether PGT-P is appropriate for your situation.

How PGT-P Is Performed

The process is similar to other PGT tests:

1. IVF cycle: Eggs are retrieved and fertilized to create embryos.
2. Embryo biopsy: A few cells are removed from the embryo, usually on day 5 or 6 (blastocyst stage).
3. Genetic analysis: The cells are analyzed to generate a polygenic risk score.
4. Embryo selection: Based on the scores, you and your doctor decide which embryos to transfer.

It is important to note that PGT-P requires a biopsy, which is an invasive procedure. While the risk is low, there is a small chance of embryo damage. Also, not all embryos may be suitable for biopsy.

Potential Benefits and Limitations

Potential Benefits

• Provides additional information about the risk of common conditions.
• May help reduce the risk of passing on polygenic diseases.
• Can be combined with PGT-A to give a more comprehensive genetic picture.

Limitations and Considerations

• Not diagnostic: A risk score is not a diagnosis. Many factors, including environment and lifestyle, influence disease development.
• Limited predictive power: For many conditions, the genetic contribution is small, so the score may not significantly change clinical management.
• Ethical concerns: There is debate about selecting embryos based on polygenic risk, as it may lead to discrimination or unrealistic expectations.
• Cost and availability: PGT-P is expensive and may not be covered by insurance. Not all clinics in Thailand offer it.
• Uncertain long-term outcomes: The technology is relatively new, and long-term health outcomes are not yet fully known.

PGT-P in Thailand: Availability and Considerations

In Thailand, PGT-P is offered at some advanced fertility centers, but it is not as widely available as PGT-A or PGT-M. The availability may depend on the clinic’s laboratory capabilities and the expertise of its genetic team.

If you are considering PGT-P in Thailand, here are some questions to ask your clinic:

• Do you offer PGT-P? If so, which conditions are included in the panel?
• What is the cost of PGT-P, and is it separate from other PGT tests?
• How many embryos are typically needed for a successful PGT-P cycle?
• What is the accuracy and validation of the risk scores?
• Do you have a genetic counselor who can explain the results?

It is also important to consider that PGT-P is not a substitute for prenatal screening or postnatal care. Even with a low-risk score, a child may still develop a condition, and a high-risk score does not mean the condition will occur.

Alternatives to PGT-P

If you are concerned about polygenic conditions, there are other options to consider:

• Preconception carrier screening: Tests parents for single-gene mutations that could be passed on.
• Prenatal testing: During pregnancy, tests like NIPT or amniocentesis can screen for certain conditions.
• Lifestyle and medical management: For many polygenic conditions, early detection and lifestyle changes can reduce risk.

Discuss these options with your healthcare provider to make an informed decision.

Questions to Ask Your Clinic

Before deciding on PGT-P, consider asking your fertility team:

• What is the scientific evidence supporting PGT-P for my specific situation?
• How will the results be used in embryo selection?
• What are the risks of embryo biopsy?
• Are there any ethical or legal considerations in Thailand?
• What is the success rate of IVF with PGT-P in your clinic?

Next Steps

If you are exploring PGT-P, here is a simple checklist:

1. Research and understand the basics of PGT-P.
2. Consult with a fertility specialist to discuss your medical history.
3. Ask if PGT-P is available and whether it is recommended for you.
4. Meet with a genetic counselor to review potential risks and benefits.
5. Consider the costs and whether you have the resources to proceed.

Remember, PGT-P is an evolving technology. Stay informed and make decisions based on the best available evidence and professional guidance.

Frequently asked questions

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

PGT-A checks for chromosomal abnormalities (aneuploidy), while PGT-P estimates the risk of polygenic conditions based on multiple genetic variants. PGT-A is more established and widely used, whereas PGT-P is newer and less commonly recommended.

Is PGT-P available in Thailand?

Yes, some fertility centers in Thailand offer PGT-P, but it is not universally available. You should check with individual clinics to see if they provide this testing and what conditions are included.

Is PGT-P recommended for everyone undergoing IVF?

No, PGT-P is not recommended for everyone. It is typically considered only in specific cases, such as a strong family history of polygenic conditions. Most professional guidelines do not endorse routine use due to limited evidence.

What are the limitations of PGT-P?

PGT-P provides only a statistical risk estimate, not a diagnosis. It has limited predictive power for many conditions, and there are ethical concerns about selecting embryos based on polygenic risk. The technology is also relatively new, so long-term outcomes are uncertain.

How much does PGT-P cost in Thailand?

The cost of PGT-P varies by clinic and is not typically covered by insurance. It is generally more expensive than PGT-A or PGT-M. You should contact clinics directly for current pricing.

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.