What Is PGT-P? Understanding Polygenic Embryo Screening in IVF
What exactly is PGT P and how is it different from other genetic testing in IVF?
Navya Muralidhar
For couples or individuals going through IVF- it’s natural to come across genetic testing such as PGT-A and PGT-M.
These are the more established forms of preimplantation genetic testing, used to look for chromosome problems or specific inherited conditions.
But PGT-P is different. It is a newer and more controversial type of testing that aims to estimate an embryo’s risk of developing common complex conditions later in life.
So why exactly is it controversial, and how does it help with IVF? We’ll talk all about it below!
What is PGT-P?
PGT-P stands for preimplantation genetic testing for polygenic conditions. You may also see it called polygenic embryo screening, or PES.
Instead of looking for one clear genetic change, it uses many small DNA markers to generate a risk score for conditions such as heart disease, diabetes, or some cancers.
That sounds sophisticated, and in many ways it is, but it is important to understand what the test can and cannot tell you.
Why PGT-P is being talked about
The idea behind PGT-P is easy to understand. If genetic differences can influence disease risk, could embryologists use that information to choose the embryo with the lowest future risk?
In theory, that sounds like a way to give IVF patients another layer of information during embryo selection.
But IVF decision-making is rarely that simple.
Patients are already balancing embryo quality, chromosome status, treatment history, age, fertility diagnosis, and emotional pressure.
Adding another score into the mix can make the process feel more precise, when in reality the evidence behind that score may still be limited. That is why PGT-P has become such a debated topic in reproductive medicine.
How PGT-P works
PGT-P starts in the same way as other embryo testing methods.
- A few cells are biopsied from a day-5 blastocyst, and the DNA from those cells is analysed in a laboratory.
- But unlike PGT-A, which checks whether an embryo has the right number of chromosomes, PGT-P is looking at thousands of small genetic variations called SNPs, or single-nucleotide polymorphisms.
These SNPs are linked in large adult population studies to disease risk. Each one contributes a tiny amount to the final score, and the result is used to estimate relative risk between embryos.
In practice, that means one embryo may be ranked as having a lower predicted risk than another for a specific condition.
But here’s the thing: It is not a diagnosis, and it is not a guarantee of future health.
Some commercial tests go a step further and combine several risk estimates into one “embryo health score.” That can make the result look even more polished, but it does not change the basic limitation: the test is still predicting, not proving.
How PGT P differs from other PGT tests
The main reason PGT-P is hard to compare with other IVF genetic tests is that it is trying to answer a very different question.
- PGT-A is used to screen for aneuploidy, which means an embryo has too many or too few chromosomes.
- PGT-SR is used when a parent carries a structural chromosomal rearrangement.
- PGT-M is used when there is a known single-gene condition in the family, such as cystic fibrosis or a specific inherited mutation.
Those tests are used for clearly defined genetic reasons.
PGT-P, on the other hand, tries to estimate risk for complex conditions that are influenced by many genes and by lifestyle, environment, and chance. That makes the interpretation far more complicated.
What are the Limitations with PGT P?
This is where PGT-P becomes more complicated than it first appears.
The issue of data discrepancy
The scores used in PGT-P were originally developed from adult population data, and much of that data comes from people of European ancestry.
That means the test may be less reliable for patients from non-European backgrounds, which is a major concern in a diverse population.
Other contributions
There is also the issue of what the test cannot account for. Disease risk is not shaped by genetics alone. Lifestyle, environment, access to healthcare, and many other factors play a major role over a person’s lifetime.
A polygenic score can only estimate inherited tendency — it cannot predict how someone will actually live, grow, or respond to the world around them.
Marginal differences between embryo scores
Another limitation is that the differences between embryos can be very small. In some cases, the scores may separate embryos by only a narrow margin, which may not translate into a meaningful real-world difference.
That is one reason many experts caution against using PGT-P to make major embryo selection decisions.
What the evidence says about PGT P
The most important point is this: PGT-P is not yet supported by enough evidence for routine clinical use.
Recent reviews and professional guidance have raised concerns about its predictive accuracy, clinical utility, and ethical implications.
ASRM’s ethics opinion states that PGT-P is a nascent and unproven technology and that current evidence does not justify using it in everyday clinical practice.
A recent narrative review also highlighted the lack of long-term outcome data and the need for much stronger validation before the test can be considered reliable.
For patients, this means the promise of PGT-P may sound more certain than the science really is. That gap between expectation and evidence is exactly why careful counselling matters.
Why PGT is being offered in current IVF cycles
PGT-P is mainly being marketed by a small number of commercial labs, especially in the US, often as an add-on to other IVF genetic tests.
In some cases, the language used makes it sound like choosing the “healthiest embryo” or reducing lifetime disease risk is already proven. But those are not outcomes that have been clearly established in clinical practice.
That can be especially difficult for IVF patients, who often want to do everything possible to improve their chances.
When a test is framed as an extra layer of protection, it can feel irresponsible to decline it. But more information is not always better if that information is uncertain or not clinically meaningful.
What regulators say about PGT P
Regulators and professional bodies have taken a cautious stance.
In the UK, the HFEA has said that PGT-P is not lawful and not supported by evidence, and that it may reduce the chances of having a baby by encouraging embryo selection based on uncertain differences. That is a strong statement, and it reflects the current regulatory position there.
In the US, ASRM has also said that PGT-P should not be used routinely and that more evidence is needed before it can be considered clinically appropriate. In both settings, the message is similar: the science is interesting, but it is not ready for standard patient care.
What to keep in mind if you’ve heard about or been offered PGT P
If PGT-P is mentioned during an IVF consultation, it is worth slowing the conversation down.
Ask what condition the test is trying to predict, how strong the evidence is, and whether the result would actually change your treatment plan. It is also reasonable to ask how the score was validated and whether it has been shown to improve live birth outcomes.
A lower-risk score does not mean an embryo will definitely result in a healthy child. A higher-risk score does not mean the baby will develop said diseases later on.
In IVF, the goal is usually to choose the embryo with the best proven chance of success, not the one with the most impressive-sounding score.
A clinician’s perspective
From a clinician or embryologist’s point of view, the most important question is whether the test helps patients make better decisions.
Right now, the answer is no, at least not in a way that has been proven consistently and safely. If a test can reduce embryo choice based on a tiny statistical difference without improving real outcomes, it may do more harm than good.
That is why most responsible fertility teams approach PGT-P carefully.
The focus should remain on established tests with clear clinical value, thoughtful counselling, and embryo selection decisions that are grounded in evidence rather than hype.
Written by
Navya Muralidhar
Navya has completed her Bachelors in Genetics and Masters in Clinical Embryology! Having worked as an embryologist for over two years, she made the shift to healthcare marketing when she realised she was an educator at heart! Now, she illustrates and breaks down complex fertility topics on Instagram, and works to create content for patients and embryologists alike!