PGT-A Testing: Who Actually Needs It — And Who Might Be Better Off Without It

The Promise — and the Confusion — Around PGT-A

If you've been through even one failed IVF cycle, chances are someone has mentioned PGT-A — preimplantation genetic testing for aneuploidies. It sounds reassuring on the surface: test your embryos before transfer, pick only the chromosomally normal ones, and improve your chances of success. But many patients leave these conversations more confused than when they started.

Is PGT-A a guarantee? Does everyone need it? And what happens if your embryos don't pass the test? These are the questions that don't always get enough time in a busy consultation — so let's work through them carefully.

What PGT-A Actually Tests For

Every human embryo should carry 46 chromosomes — 23 pairs. When an embryo has too many or too few chromosomes, it's called aneuploid. Most aneuploid embryos either fail to implant, result in an early miscarriage, or in some cases lead to conditions like Down syndrome (trisomy 21).

PGT-A involves taking a small biopsy of cells from the outer layer of a blastocyst (the embryo at day 5 or 6 of development) and sending those cells to a genetics lab. The lab analyses all 23 chromosome pairs and reports back whether the embryo is:

• Euploid — chromosomally normal, suitable for transfer
• Aneuploid — chromosomally abnormal, not recommended for transfer
• Mosaic — a mixture of normal and abnormal cells, requiring a more nuanced conversation

The intention is to transfer only euploid embryos, theoretically reducing the chance of failed cycles and miscarriage.

When PGT-A Makes Real Clinical Sense

PGT-A is not a universal upgrade. It works best when there is a genuine, evidence-backed reason to suspect a higher rate of chromosomal abnormality in your embryos. Your doctor at Iswarya Fertility may recommend discussing PGT-A more seriously in the following situations:

Advanced Maternal Age (Typically 37 and Above)

Egg quality declines with age, and with it, the rate of chromosomal errors rises significantly. By the early 40s, the majority of embryos may be aneuploid. For women in this age group with multiple blastocysts available, PGT-A can help identify which embryos are worth transferring first — potentially reducing the number of failed transfers before a successful pregnancy.

Recurrent Implantation Failure

If you've had two or more good-quality embryos transferred without achieving a pregnancy, chromosomal abnormality is one possible explanation. PGT-A can help rule this in or out, especially when the uterus has already been evaluated and found to be normal.

Recurrent Pregnancy Loss

For patients who have experienced three or more miscarriages, chromosomal abnormality in the embryo is a leading cause. PGT-A may help select embryos less likely to result in another loss — though it's worth knowing that testing the embryo is only one piece of a broader investigation.

Previous Pregnancy With Chromosomal Abnormality

If a prior pregnancy was confirmed to have a chromosomal condition, PGT-A adds an extra layer of screening in future IVF cycles.

When PGT-A May Not Be Necessary — Or Could Even Work Against You

This is the part that often surprises patients. PGT-A is sometimes recommended more broadly than the evidence supports — and for certain patients, it may reduce rather than improve the chance of success.

Consider a woman in her late 20s or early 30s with good ovarian reserve, no history of miscarriage, and several high-quality blastocysts after her first IVF cycle. In this scenario, the natural rate of euploidy is already high. Adding PGT-A means biopsying embryos (which carries a small but real risk of damage), waiting for results, and potentially discarding embryos that might have implanted successfully.

There is also the important issue of mosaic embryos. Early PGT-A classifications treated all mosaic results as non-transferable. We now know that many mosaic embryos can result in healthy pregnancies — but only if they're given the chance. Blanket discard policies based on PGT-A results have likely cost some patients viable pregnancies.

For patients with a limited number of blastocysts, the maths can also work against you. If you have two blastocysts and both come back aneuploid, you are left with nothing to transfer. Without testing, at least one might have implanted. It's a genuinely difficult calculation, and one worth discussing openly with your fertility specialist.

The Mosaic Grey Zone: What It Means and What to Do

Mosaic embryos — those with a mix of chromosomally normal and abnormal cells — represent one of the most nuanced areas of modern IVF. They are not straightforwardly aneuploid, but they are also not the same as fully euploid embryos.

Current international guidelines suggest that mosaic embryos can be considered for transfer after euploid embryos have been used, under careful counselling. The outcomes for low-level mosaic embryos are reasonably good, and blanket rejection of these embryos is no longer considered best practice at well-informed fertility centres.

The team at Iswarya Fertility takes a personalised approach to mosaic embryo counselling — helping patients understand the specific type of mosaicism, the chromosomes involved, and what the latest evidence suggests for their individual case.

Questions Worth Asking Before You Agree to PGT-A

If your doctor recommends PGT-A, or if you're wondering whether to request it, here are some questions that will help you have a more informed conversation:

1. Given my age and history, what percentage of my embryos is likely to be euploid without testing?
2. How many blastocysts do we expect to have available for testing?
3. What will we do if all embryos come back aneuploid or mosaic?
4. Does your lab have experience with mosaic embryo counselling and transfer?
5. Will PGT-A results change our transfer strategy in a meaningful way for my specific case?

Good answers to these questions will tell you a great deal about whether PGT-A is genuinely the right next step for you.

Making the Right Decision for Your Journey

PGT-A is a powerful tool — but like any tool, its value depends entirely on using it in the right situation. For some patients, it genuinely improves outcomes and reduces heartbreak. For others, it adds cost and complexity without meaningfully changing the path forward.

If you're unsure whether PGT-A is right for your IVF journey, the specialist team at Iswarya Fertility can walk you through the evidence as it applies to your specific history, embryo numbers, and fertility goals — so that whatever you decide, you decide with clarity.

Frequently Asked Questions

Is PGT-A testing compulsory for IVF?

No, PGT-A is optional and not necessary for every patient. It is most beneficial for women over 37, those with recurrent miscarriage, or patients who have had multiple failed transfers. Your fertility specialist will recommend it only when the evidence supports it for your specific situation.

Does PGT-A guarantee a successful pregnancy?

No. PGT-A improves the odds of transferring a chromosomally normal embryo, but it does not guarantee implantation or a live birth. Factors like uterine receptivity, embryo quality beyond chromosomes, and individual health also play important roles.

What happens if all my embryos are aneuploid after PGT-A?

If all embryos test as aneuploid, your doctor will typically recommend another stimulation cycle to create new embryos. In some cases, mosaic embryos — which fall between normal and abnormal — may be considered for transfer after careful counselling.

Can a mosaic embryo result in a healthy baby?

Yes. Studies show that low-level mosaic embryos can and do result in healthy pregnancies and births. They are generally considered for transfer only after fully euploid embryos have been used, and require detailed counselling about the specific chromosomes involved.

Does the embryo biopsy for PGT-A damage the embryo?

In experienced hands, the risk is very low. The biopsy removes a few cells from the outer layer of the blastocyst — the cells that will become the placenta, not the baby itself. Clinics with skilled embryologists and high biopsy volumes have the best safety records for this procedure.