One of the questions I am increasingly asked by patients undergoing IVF is:
“Should I test my embryos?”
It sounds like a simple question. But my answer is rarely an automatic yes or no.
PGT-A — preimplantation genetic testing for aneuploidy — can provide valuable information about embryos before transfer. But whether that information is likely to benefit you depends on much more than whether the test is available.
Your age matters. Your number of embryos matters. Your previous pregnancies and miscarriages matter. Cost matters. But your fears, priorities, family history and what you have already experienced on your fertility journey matter too. That is why I believe the better question is not simply “Does PGT-A work?” It is: “What are we hoping PGT-A will achieve for this particular patient?”
What is PGT-A?
PGT-A is a genetic test performed on embryos created through IVF.
How the biopsy is performed
At the blastocyst stage, usually around day 5 or 6 of development, a small number of cells are biopsied from the part of the embryo that will contribute to the placenta. These cells are analysed to assess the number of chromosomes present.
Euploid, aneuploid and mosaic explained
An embryo with the expected number of chromosomes is described as euploid. An embryo with an abnormal number is described as aneuploid. Aneuploid embryos are less likely to implant, more likely to miscarry and, in some circumstances, can result in a pregnancy affected by a chromosomal condition. PGT-A can therefore help us decide which embryo to prioritise for transfer.
But there is an important distinction: PGT-A selects embryos. It does not make an embryo healthier or change an abnormal embryo into a normal one.
Does PGT-A increase the chance of having a baby?
This is where the evidence becomes particularly important.
One of the landmark studies was published in the New England Journal of Medicine in 2021. The randomised trial involved 1,212 women aged 20–37 who had at least three good-quality blastocysts.
The cumulative live-birth rate was:
- 77.2% with PGT-A
- 81.8% with conventional IVF
Pregnancy loss, however, was lower with PGT-A:
- 8.7% with PGT-A
- 12.6% with conventional IVF
The study therefore demonstrated something I think is very important for patients to understand:
Reducing unsuccessful pregnancies or improving embryo selection is not necessarily the same as increasing the total chance of taking home a baby from one IVF egg collection.
This is one reason I do not routinely recommend PGT-A to every patient undergoing IVF.
So when might PGT-A be useful?
The answer becomes much more individual. Consider two very different patients. A 32-year-old woman with several good-quality embryos, no history of miscarriage and no particular genetic concerns may have a relatively low risk of embryo aneuploidy.
If she asks for PGT-A simply because she has read online that “tested embryos are better”, I would spend time explaining the evidence before recommending another procedure and additional cost.
Now consider a woman approaching 40 who has produced four or five blastocysts. Her situation is different. The likelihood of embryo aneuploidy increases substantially with maternal age. PGT-A may therefore provide useful information for prioritising which embryo to transfer and potentially avoiding some transfers of aneuploid embryos. It does not guarantee a baby. But avoiding several unsuccessful transfers or miscarriages may itself be extremely meaningful to that patient.
Sometimes the patient’s individual story changes the decision
Age and statistics aren’t the entire consultation. I once saw a woman in her early 30s whose sister had a child with Down syndrome. Statistically, she was young and at relatively low age-related risk of embryo aneuploidy. But emotionally and personally, this issue carried enormous significance for her. She was already undergoing IVF, and reducing the possibility of transferring an embryo with a detectable chromosome abnormality was extremely important to her.
That is very different from another 32-year-old requesting PGT-A simply because she saw it recommended online. After appropriate counselling about what PGT-A can and cannot tell us, its limitations and its costs, I would support the first patient’s decision to test. Evidence-based medicine should not mean treating every patient with the same statistic. The evidence informs the conversation. The patient’s individual circumstances help determine the decision.
What about recurrent miscarriage?
This is another situation where the discussion becomes more complex.
A significant proportion of early miscarriages are associated with chromosomal abnormalities in the embryo. For someone who has experienced recurrent miscarriage — particularly at an older reproductive age — identifying euploid embryos before transfer may therefore be attractive.
But again, PGT-A should not automatically be offered simply because somebody has experienced miscarriage.
There are other causes of pregnancy loss, and transferring a euploid embryo cannot eliminate them.
There is also another issue that I discuss with patients who have already endured repeated miscarriages.
Miscarriage is not simply another unsuccessful embryo transfer. It can mean weeks or months of pregnancy followed by loss. Some women undergo repeated surgical procedures to manage those pregnancies. In a small number, repeated uterine procedures can contribute to intrauterine adhesions, including Asherman syndrome.
By the time we eventually identify and transfer a chromosomally suitable embryo, we may therefore be dealing with additional reproductive issues that were not present at the beginning of the journey.
So for some patients, reducing the number of miscarriages may matter even if PGT-A has not been shown to increase cumulative live-birth rates overall. That distinction deserves to be part of informed decision-making.
There is also a potential downside to testing
PGT-A is not simply a blood test. Cells must be biopsied from the embryo. Modern blastocyst biopsy is performed by highly trained embryologists and many biopsied embryos go on to produce healthy babies. Nevertheless, the procedure is invasive. I explain it to patients this way: The biopsy does not make the embryo better. We perform it because the information we gain may be valuable.
Therefore, the potential value of that information should justify the intervention. There are also limitations to the test itself. The few cells sampled from the trophectoderm do not necessarily represent every cell within the embryo. Some embryos receive a mosaic result, meaning the sample contains a mixture of apparently normal and abnormal chromosome signals. Mosaic embryos can sometimes result in healthy babies. This creates an important risk: an embryo with reproductive potential could potentially be deprioritised or discarded because of the way its biopsy result is interpreted. These possibilities should be discussed before testing, rather than only when an unexpected result arrives.
And we need to talk about cost
PGT-A adds another expense to an already expensive IVF journey. Cost therefore belongs in the medical conversation. If testing is unlikely to meaningfully alter management for a particular patient, I think we need to ask whether that money is providing genuine clinical value. For another patient — perhaps an older woman with multiple blastocysts who places enormous importance on reducing unsuccessful transfers — the same expense may represent very different value. Again, there is no universal answer.
What do the major professional bodies say?
The American Society for Reproductive Medicine concluded in its 2024 committee opinion that the value of PGT-A as routine screening for all IVF patients has not been demonstrated and that routine use in every infertile patient cannot currently be recommended. The UK’s Human Fertilisation and Embryology Authority similarly distinguishes between two outcomes that patients often assume are the same. For most fertility patients, it currently rates PGT-A red for improving the chance of having a baby, while rating it green for reducing miscarriage. That distinction closely reflects how I think we should discuss PGT-A clinically.
The question I ask before recommending PGT-A
When a couple asks me:
“Should we test our embryos?”
I first want to understand the couple in front of me.
- How old are they?
- How many embryos are we likely to have?
- What has happened in previous IVF cycles?
- Have there been miscarriages?
- Is there a relevant family or reproductive history?
- What are they frightened of?
- What matters most to them?
- How would they feel about another miscarriage compared with another unsuccessful embryo transfer?
- How would they feel if testing left them with no embryo recommended for transfer?
- What would the additional cost mean for them?
And importantly:
What are they hoping the test will give them?
Only then can we decide whether the potential benefit of PGT-A outweighs its costs, limitations and potential risks.
My view on PGT-A
I don’t believe PGT-A should be an automatic yes. I don’t believe it should be an automatic no either.
For a young patient with a good prognosis, routine testing may add cost and complexity without improving her cumulative chance of having a baby. For an older patient with several blastocysts, a patient with particular reproductive circumstances, or someone for whom avoiding an aneuploid pregnancy or potentially reducing miscarriage is especially important, the balance may look very different. PGT-A is a sophisticated tool.
But sophisticated technology is most useful when we are clear about the problem we are asking it to solve.
The evidence should guide us. The patient’s individual clinical situation should guide us. And the patient’s values, fears and priorities should be part of that decision too.That is what individualised fertility care should look like.
Key references
Yan J, et al. Live Birth with or without Preimplantation Genetic Testing for Aneuploidy. New England Journal of Medicine. 2021;385:2047–2058. doi:10.1056/NEJMoa2103613.
American Society for Reproductive Medicine Practice Committee. The use of preimplantation genetic testing for aneuploidy: a committee opinion. Fertility and Sterility. 2024.
Human Fertilisation and Embryology Authority. Pre-implantation genetic testing for aneuploidy (PGT-A). Treatment Add-ons.
American Society for Reproductive Medicine Practice Committee and Genetic Counseling Professional Group. Clinical management of mosaic results from preimplantation genetic testing for aneuploidy of blastocysts: a committee opinion. Fertility and Sterility. 2023;120:973–982.
This article provides general information about fertility treatment and should not replace individual medical advice. Whether PGT-A is appropriate depends on each patient’s clinical circumstances and should be discussed with their fertility specialist.