Does PGT-A really improve IVF success? Here’s what the evidence says

IVF is a process that involves so many important decisions. For some patients, one of those decisions is whether to include additional genetic testing.

PGT-A (Preimplantation Genetic Testing for Aneuploidy) has become one of the most widely discussed developments in fertility treatment, and it’s easy to see why.

If you can identify the embryo most likely to succeed, surely that increases your chance of having a baby?

In reality, it’s a bit more complicated. While PGT-A may offer clear advantages for some patients, current evidence suggests it isn’t beneficial for everyone.

Here’s everything you need to know about PGT-A and whether it’s right for you.

PGT-A at a glance

• PGT-A doesn’t improve embryo quality. Instead, it provides information about chromosome number.
• PGT-A is rated green by the HFEA for reducing the risk of miscarriage in most fertility patients, based on high-quality evidence. It is rated red for improving the overall chance of having a baby, meaning current evidence does not show it improves treatment effectiveness for this outcome.
• Current evidence doesn’t support routine PGT-A for all IVF patients.
• Whether PGT-A is right for you depends on your age, fertility history and treatment circumstances.

What is PGT-A?

PGT-A, also known as PGS (Preimplantation Genetic Screening), is designed to help patients understand the genetic health of an embryo before embryo transfer.

The first stage involves patients undergoing an IVF process to create embryos for testing. Once the embryos have been created, a small sample of between five and ten cells is taken from the outside of each embryo for testing.

The embryos are then frozen while the PGT-A test is carried out.

Using Next Generation Sequencing (NGS) technology, all chromosomes of the sample cells from a Day 5 or 6 embryo are examined, and any abnormalities are revealed.

These results help identify which embryos are more likely to be chromosomally normal (euploid), providing additional information to help guide decisions about which embryo to transfer in a future treatment cycle.

The whole screening process usually takes around two weeks. Once the results have been returned, your consultant discusses the findings with you and puts a treatment plan in place.

Why chromosome abnormalities matter

An embryo needs the correct number of chromosomes to support normal development.

Even if fertilisation occurs successfully, an incorrect chromosome number can prevent implantation altogether or cause development to stop very early, sometimes before a pregnancy is even recognised.

Chromosomal abnormalities are one of the most common reasons embryos fail naturally and miscarriages occur.

Many embryos that appear healthy under the microscope may still carry chromosomal abnormalities that can’t be detected visually.

What is PGT-A designed to achieve?

One of the biggest misconceptions about PGT-A is that it can make embryos healthier. Unfortunately, that’s not the case. PGT-A doesn’t change an embryo’s genetic makeup or improve its quality.

Instead, by analysing a small sample of cells taken during an embryo biopsy, PGT-A helps embryologists identify embryos that are more likely to have the correct number of chromosomes.

This information can help guide decisions about which embryo to transfer first, particularly when several embryos are available.

It’s also important to remember that an embryo’s appearance and its chromosome status aren’t always the same. An embryo that looks good under the microscope may still have chromosomal abnormalities.

On the other hand, one with a more average appearance may be euploid, meaning it has the normal complement of 46 chromosomes (23 pairs) and is more likely to have the potential to develop into a healthy pregnancy.

Does PGT-A improve IVF success?

PGT-A may reduce the risk of miscarriage for some patients, but current evidence doesn’t show that it increases the overall chance of having a baby for everyone undergoing IVF.

That’s why recommendations vary between patients and why researchers haven’t yet reached a simple yes or no conclusion.

Here are a few reasons why:

1. The patients being studied aren’t all the same

One of the biggest challenges when interpreting research is that IVF patients are incredibly diverse. A woman in her early 30s going through her first round of IVF is in a very different situation to someone in their early 40s who’s experienced recurrent miscarriage or several unsuccessful embryo transfers.

Younger patients are also less likely to produce embryos with chromosome abnormalities, so they may gain less from PGT-A than older patients, where aneuploidy (an abnormal number of chromosomes) is more common. When studies combine these groups, any benefit seen in one group can be diluted by the other. It’s also worth noting that evidence specifically for older patients remains limited, and the HFEA currently rates several outcomes for this group as inconclusive rather than proven.

2. Researchers measure success in different ways

Some researchers interpret success differently. Some studies look at the chance of pregnancy after a single embryo transfer, while others measure the overall live birth rate from one complete IVF cycle, including all fresh and frozen embryo transfers. Others focus on miscarriage rates or the time taken to achieve a pregnancy.

These are all valid outcomes, but they answer different questions. A treatment that reduces the number of unsuccessful embryo transfers, for example, won’t necessarily increase the overall chance of having a baby from a full IVF cycle.

3. Results can vary between clinics

PGT-A relies on several stages of the IVF process, including embryo culture, biopsy and genetic analysis. The expertise of the embryology laboratory, along with the techniques used, can all influence outcomes.

This means results reported by one clinic or research centre may not always be directly applicable elsewhere, making it difficult to compare studies or draw universal conclusions.

Overall, current evidence suggests that PGT-A may reduce the risk of miscarriage for carefully selected patients, particularly those at higher risk of producing embryos with chromosomal abnormalities or those with several embryos available for selection.

However, large reviews and professional guidelines have not found sufficient evidence to recommend routine PGT-A for all IVF patients as a way of improving live birth rates.

This is reflected in the HFEA’s traffic light system, which does not recommend PGT-A as an routine IVF add-on to increase the chance of having a baby for most patients. However, it does recognise that PGT-A may reduce the risk of miscarriage for some patients, highlighting the importance of individual assessment.

Most experts agree that the decision should be based on an individual’s age, fertility history and treatment goals.

Who might benefit from PGT-A?

PGT-A isn’t routinely recommended for everyone undergoing IVF. Whether it’s likely to benefit you depends on factors such as your age, fertility history and the number of embryos available.

Dr Wael Saab, fertility consultant and senior medical director at CRGH, says:

“One of the biggest misconceptions about PGT-A is that it’s something every IVF patient should have. In reality, it’s a valuable tool when it’s used for the right reasons and with the right patients. Our role is to help each patient understand whether the additional information it provides is likely to influence their treatment.”

For example, someone who produces eight or ten blastocysts may benefit more from PGT-A because there are multiple embryos to choose from. The additional genetic information can help prioritise which embryo to transfer first.

Depending on individual circumstances, PGT-A may be considered for patients in the following groups:

Patients where age-related chromosome changes may be more likely

As female age increases, so does the likelihood of embryos having an abnormal number of chromosomes. Because of this, PGT-A may help identify embryos that are chromosomally normal (euploid), potentially reducing the number of unsuccessful transfers and the risk of miscarriage in some patients.

Patients with recurrent miscarriage

Repeated miscarriages can have many different causes, but chromosomal abnormalities are one recognised factor. If previous pregnancy losses are thought to be related to embryo aneuploidy, PGT-A may help identify embryos with the correct number of chromosomes for transfer. However, it’s important to remember that not all miscarriages are caused by chromosomal abnormalities, so PGT-A won’t be appropriate or beneficial in every case.

Recurrent implantation failure

For patients who have experienced several unsuccessful embryo transfers despite having good-quality embryos, PGT-A may be considered as part of a broader assessment. While implantation depends on many factors (including the uterus and endometrial environment as well as the embryo itself), confirming an embryo’s chromosome status may provide additional information to guide treatment.

Patients with several embryos available

The more embryos available, the more valuable a selection tool can become. When there are multiple blastocysts, PGT-A can provide additional information to help determine the order in which embryos are transferred. For patients with only one or two embryos, the test may be less likely to change the treatment plan.

What should you know before deciding on PGT-A?

Deciding whether to have PGT-A is a personal choice, and understanding what the process involves can help you feel more informed.

While the test can provide useful insights into embryo chromosome status, there are some important things to consider:

Not every embryo can be tested

PGT-A is carried out when an embryo reaches the blastocyst stage, usually on day five or six of development. However, not every embryo will continue developing to this stage, which means some embryos won’t be suitable for testing.

If only one or two embryos are available, PGT-A may provide less useful information because there are fewer embryos to compare. Your fertility specialist will discuss whether testing is likely to influence your treatment plan before recommending it.

Understanding mosaic embryos

This is where things get a bit more technical. Sometimes the results aren’t simply “normal” or “abnormal”. An embryo may be described as mosaic, which means it contains a mixture of cells with the expected number of chromosomes and cells with chromosomal abnormalities.

As our understanding of mosaic embryos has evolved, so has clinical practice. Some mosaic embryos have gone on to result in healthy pregnancies and live births, although their chances of implantation are generally lower than those of fully euploid embryos.

Deciding whether a mosaic embryo is suitable for transfer depends on the type and level of mosaicism, as well as your individual circumstances, so these decisions are made on a case-by-case basis.

PGT-A is a highly accurate screening test, but not a guarantee

Although PGT-A provides valuable information about chromosome number, it can’t guarantee whether an embryo will implant or result in the birth of a healthy baby.

That’s because only a small number of cells are removed from the trophectoderm – the part of the embryo that later develops into the placenta.

While this provides an excellent indication of the embryo’s chromosome status, it may not perfectly represent every cell within the embryo. In addition, many other factors influence whether a pregnancy is successful, including the uterine environment and embryo development after transfer.

Additional costs and treatment planning

Because PGT-A involves embryo biopsy, genetic analysis and freezing embryos while the results are processed, it increases the overall cost of IVF treatment. It may also mean having a frozen embryo transfer rather than a fresh transfer.

For patients who are likely to benefit from the additional information PGT-A provides, these extra steps may be worthwhile. For others, they may not change the overall treatment plan.

This is why your consultant will discuss the potential benefits and drawbacks based on your individual circumstances before recommending the test.

Questions to ask your fertility specialist

Opting for PGT-A is a personal decision and your fertility specialist can help explain how it fits into your overall treatment plan.

You may find it helpful to ask:

• Am I likely to benefit from PGT-A based on my age and fertility history?
• How many embryos would I be expected to produce and would PGT-A influence which embryo is transferred first?
• What are the potential advantages and disadvantages in my situation?
• If the results show that none of my embryos are euploid, what would my options be?
• How will PGT-A affect the cost and timing of my IVF treatment?
• Is there any reason you would recommend against PGT-A in my case?
• What happens if none of my embryos are suitable for transfer?

Is PGT-A right for you?

PGT-A has become an important tool in modern fertility treatment, but it isn’t the right choice for every patient. Rather than improving embryo quality, it provides additional genetic information that can help guide embryo selection in certain situations.

For some patients, this may reduce the number of unsuccessful embryo transfers or lower the risk of miscarriage. For others, current evidence suggests it may not improve the overall chance of having a baby.

The decision to have PGT-A should always be based on your individual circumstances, including your age, fertility history and the number of embryos available. Discussing the potential benefits and limitations with an experienced fertility specialist can help you decide whether it’s likely to add value to your treatment.

If you’re considering IVF and would like to understand whether PGT-A could play a role in your treatment, speak to your CRGH consultant or arrange an initial consultation. We’ll take the time to explain your options, answer your questions and help you decide whether genetic testing is likely to benefit your individual circumstances.

If you’d like to learn more about PGT-A screening at CRGH, you can find further information here.