PGT-A for Advanced Maternal Age: What the Evidence Shows

If you are in your late 30s or 40s, PGT-A (preimplantation genetic testing for aneuploidy) will probably be offered to you, and often presented as the obvious choice. The case for it sounds simple: more embryos are chromosomally abnormal at older ages, so testing should help you avoid transfers that will not work. The trial evidence is more mixed than that. This article sets out what the studies in older patients actually found, why results look very different depending on how you count them, and how to tell whether you are the kind of patient most likely to benefit.

Why age is the core of the argument

As egg age rises, so does the chance that an embryo has the wrong number of chromosomes. Those embryos are the ones PGT-A tries to identify before transfer. In the STAR trial, cited in the American Society for Reproductive Medicine's 2024 committee opinion, 52.0% of biopsied embryos were aneuploid in women under 35. In women aged 35 to 40 the figure was 64.5% (ASRM Practice Committee, 2024).

That rising rate is real. The catch is that PGT-A cannot make an embryo normal. It can only identify which embryos to use and which to set aside. Whether that improves your chance of a baby depends on whether it helps you find the good embryo faster, without losing good embryos along the way.

What the studies in older patients found

ASRM also notes that in the Rubio trial's later frozen transfers, outcomes were similar between groups (37% vs 33.3%, not significant). Its overall conclusion is that PGT-A "may have a beneficial role" in older patients, particularly with good ovarian reserve, but that its value as a universal test has not been shown.

The UK regulator, the HFEA, reaches a more cautious view for this group. It rates PGT-A grey for older women, meaning there is not enough moderate or high-quality evidence to say whether it improves the chance of a baby or reduces miscarriage. It rates PGT-A red for raising birth rates in most patients, because testing often leaves fewer embryos to transfer and time to birth may be longer (HFEA, 2023).

The denominator problem

The same treatment can look like a big improvement or no improvement, depending on what you divide by.

• Per transfer. PGT-A usually looks best here. By the time you reach transfer, abnormal embryos have been filtered out, so each transfer has better odds.
• Per started cycle or retrieval. This counts everyone, including people who end up with no normal embryo and so no transfer. In older patients, that group can be large.
• Cumulative. This adds up every transfer from a retrieval. Testing does not create extra viable embryos, so if every embryo would eventually have been transferred anyway, the total number of babies from that retrieval may not change much. The difference is how many transfers and miscarriages it takes to get there.

So when a clinic says PGT-A "doubles success" for women over 40, ask: per transfer, or per retrieval?

Where PGT-A may help older patients most

The potential benefits are practical as well as statistical:

• Fewer failed transfers. Each transfer that does not work costs time, money and emotional energy. Avoiding transfers of embryos that cannot succeed can shorten the road for some people.
• Fewer miscarriages. The HFEA rates PGT-A green for reducing miscarriage in most patients, though it does not remove the risk and rates the evidence in older women as grey. ASRM calls the effect on miscarriage "unclear."
• Better-informed decisions. If several retrievals produce only abnormal embryos, that information can help you decide whether to keep going or consider donor eggs.

ASRM's wording, "especially with good ovarian reserve," matters. Testing tends to make more sense when you have several blastocysts to choose between. With many embryos, selection does real work. With one or two, there is little to select, and the risks below weigh more heavily.

An illustrative example

The following is a hypothetical example to show how the decision plays out, not a prediction for any patient. Imagine a 41-year-old whose retrieval produces four blastocysts, and suppose, for illustration, that one of the four is chromosomally normal.

• Without testing, she might transfer the embryos one at a time, ranked by grade. If the normal embryo happens to be ranked third, she may go through two failed transfers or miscarriages before reaching it. Each takes weeks to months.
• With testing, the normal embryo is identified first and transferred first. If the test is accurate, she reaches the same embryo with fewer transfers and less time.
• The risk is that the test misreads the normal embryo as abnormal, or the biopsy harms it. Then testing has removed her only chance from that retrieval.

In this example, testing changes the route, not the number of normal embryos. Whether that trade is worth making depends on how many embryos you have, how much time you have, and how you weigh repeated transfers and miscarriages against the risk of losing a viable embryo.

The trade-offs that matter more at older ages

• No transfer at all. If every tested embryo is reported abnormal, you will have nothing to transfer from that cycle. In the Rubio trial, almost a third of PGT-A patients did not reach transfer.
• Wrong results. The HFEA warns that PGT-A can miss an abnormality or report one that is not there, so healthy embryos may be discarded.
• Mosaic and no-result embryos. Some embryos are reported as mosaic, or give no result. Clinic policies on using them vary. ASRM reports inconclusive results in 0.86% to 3.8% of biopsies. Our guide to mosaic embryos explains the options.
• Biopsy effects. Removing cells may damage an embryo. ASRM notes trophectoderm biopsy at the blastocyst stage has less impact than older cleavage-stage biopsy, but the effect is not fully understood.
• A frozen transfer. Testing usually means freezing all embryos and transferring in a later cycle, which adds time.

Is PGT-A worth it for you? Questions to work through

• How many blastocysts do you expect from a retrieval at my age and ovarian reserve?
• What is my chance of having no normal embryo to transfer after testing?
• When you quote success with PGT-A, is it per transfer, per retrieval or cumulative?
• Would I transfer every embryo anyway if I did not test?
• What is your policy on mosaic and no-result embryos, and is it written down? ASRM recommends a written policy for abnormal embryos.
• If I bank embryos over several retrievals, can I test them together?

For the wider debate across all ages, see PGT-A: the evidence debate. For the bigger picture on treatment choices after 40, our guide to IVF at 40 and beyond sets PGT-A alongside banking and donor eggs.

PGT content on this site is limited to chromosomal screening (PGT-A) and testing for known genetic conditions (PGT-M/PGT-SR). It does not cover sex selection or non-medical trait selection.

Frequently asked questions

Does PGT-A increase my chance of having a baby if I am over 40?

It can increase the chance per transfer. Whether it increases the overall chance from a retrieval is not established. ASRM says it may help some older patients, especially with good ovarian reserve, and the HFEA rates the evidence for older women as insufficient.

Will PGT-A prevent miscarriage?

It may lower the risk, but it does not remove it. The HFEA rates PGT-A green for reducing miscarriage in most patients but grey for older women, and ASRM describes the effect as unclear.

What if all my embryos come back abnormal?

Then there is no transfer from that cycle. That is a real risk at older ages, and it is worth discussing in advance how you would decide between another retrieval and other options, such as donor eggs.

Is PGT-A recommended for every IVF patient over 35?

No. ASRM does not recommend routine PGT-A for all IVF patients, and its 2024 opinion advises individual decisions based on age, ovarian reserve and number of embryos.

Do I need ICSI if I choose PGT-A?

Not routinely. ASRM's 2024 opinion states ICSI is not needed simply because embryos will be tested, although it may be used for other reasons.

Sources

• ASRM Practice Committee — The use of PGT-A: a committee opinion (Fertil Steril, 2024)
• HFEA — Pre-implantation genetic testing for aneuploidy (PGT-A) (2023)