PGT-A in Plain English — Should You Test Your Embryos?

Pre-implantation Genetic Testing for Aneuploidy, or PGT-A as it's more commonly known, is a topic that frequently comes up in my consultations with patients begin their IVF journey. It's often presented as a revolutionary step, a 'must-have' for a successful pregnancy, but like many powerful medical technologies, its application requires careful consideration and a clear understanding of what it can, and cannot, achieve.

What Exactly is PGT-A, and Why Do We Do It?

At its core, PGT-A is a genetic test performed on embryos created through In Vitro Fertilisation (IVF) before they are transferred into the womb. Its purpose is to screen these embryos for aneuploidies, which are numerical chromosomal abnormalities. Think of it like this: a normal human cell has 46 chromosomes, arranged in 23 pairs. An aneuploid embryo has either too many or too few chromosomes, for instance, an extra copy of chromosome 21 (Down syndrome), or a missing X chromosome (Turner syndrome). These chromosomal errors are the leading cause of IVF failure, miscarriages, and the birth of a child with a genetic syndrome.

The rationale behind PGT-A is compelling: by identifying and preferentially transferring euploid (chromosomally normal) embryos, we aim to improve implantation rates, reduce miscarriage rates, and decrease the time to a successful pregnancy. This sounds ideal, doesn't it? However, the reality is more nuanced, and it's crucial for my patients in Hyderabad and elsewhere to understand these subtleties.

How is PGT-A Performed? A Peek Behind the Curtain

The process begins with an IVF cycle where eggs are retrieved and fertilised to create embryos. These embryos are then cultured in the laboratory, typically until they reach the blastocyst stage, which is around day five or six after fertilisation. At this stage, the embryo has differentiated into two main parts: the inner cell mass (which will become the baby) and the trophectoderm (which will form the placenta).

A highly skilled embryologist performs a biopsy, carefully removing a small number of cells (typically 5-10) from the trophectoderm using a laser. This is a delicate procedure that requires precision and experience. Crucially, the inner cell mass is left untouched, minimising any potential harm to the developing embryo. The biopsied cells are then sent to a specialised genetics laboratory for analysis, while the embryos themselves are cryopreserved (frozen) to await the test results.

Once the genetic analysis is complete, the results categorise embryos as euploid (normal), aneuploid (abnormal), or mosaic (a mix of normal and abnormal cells). Based on these results, and after a thorough discussion with me, patients can then make an informed decision about which embryos to transfer.

Who Stands to Benefit Most from PGT-A?

While PGT-A is often broadly marketed, the scientific evidence suggests specific groups of patients derive the most significant benefit. In my practice at Apollo Fertility, I typically recommend PGT-A for:

• Advanced Maternal Age. This is arguably the strongest indication. As women age, the quality of their eggs declines, leading to a higher incidence of aneuploid embryos. For women over 35, and especially over 38-40, the proportion of aneuploid embryos can be very high. PGT-A helps identify the rare normal embryos, avoiding futile transfers of abnormal ones.

• Recurrent Implantation Failure (RIF). Patients who have experienced multiple failed IVF cycles despite transferring good-quality embryos often find PGT-A helpful. It helps rule out aneuploidy as a contributing factor to their previous failures.

• Recurrent Pregnancy Loss (RPL). Similar to RIF, if a patient has had two or more miscarriages, especially early miscarriages, PGT-A can help identify if chromosomal abnormalities in the embryo were the cause, thus guiding future IVF attempts.

• Severe Male Factor Infertility. Some studies suggest a potential benefit in cases of severe male factor infertility, as sperm quality can sometimes be associated with embryo chromosomal abnormalities.

• Previous Aneuploid Pregnancy. For couples who have previously conceived a pregnancy with a chromosomal abnormality (e.g., a child with Down syndrome, or a miscarriage due to aneuploidy), PGT-A can help reduce the risk of recurrence in future IVF cycles.

It's important to understand that for younger patients with a good prognosis and their first IVF cycle, the benefits of PGT-A are less clear-cut and are still a subject of ongoing research and debate. It might not significantly improve live birth rates per embryo transfer in these groups, though it could potentially shorten the time to pregnancy by avoiding transfers of abnormal embryos.

The Nuance of Mosaicism: A Complex Consideration

One of the most significant developments, and indeed complexities, in PGT-A has been the recognition and interpretation of mosaicism. A mosaic embryo contains a mixture of both euploid (normal) and aneuploid (abnormal) cells. When PGT-A first emerged, embryos were largely categorised as simply 'normal' or 'abnormal'. However, with improved resolution of testing, we now detect these 'mixed' embryos.

The presence of mosaicism complicates counselling and decision-making. While mosaic embryos generally have a lower implantation potential and a higher miscarriage rate compared to euploid embryos, they can, in some cases, lead to a healthy live birth. This is thought to be due to the body's ability to 'self-correct' (the normal cells outgrow the abnormal ones) or because the abnormal cells are sequestered into the placenta and don't affect the foetus. Prioritising euploid embryos is always the first choice, but in situations where no euploid embryos are available, transferring a low-level mosaic embryo might be considered after thorough discussion about the risks and benefits.

Potential Downsides and Considerations

While PGT-A offers significant advantages for selected patients, it's not without its drawbacks and points for careful consideration:

• Cost. PGT-A adds a substantial cost to an already expensive IVF cycle. In India, the cost for PGT-A analysis typically ranges from INR 30,000 to INR 60,000 per embryo, depending on the clinic and the laboratory performing the analysis, plus the cost of the biopsy itself which is often included in the IVF package or charged separately. For patients with many embryos, this can quickly add up, and it's usually not covered by health insurance.

• Embryo Biopsy Risk. Although generally safe in experienced hands, there's a theoretical, albeit low, risk of damaging the embryo during the biopsy procedure. This risk is minimised at reputable centres like Apollo Fertility with highly skilled embryologists.

• False Positives/Negatives. No test is 100% perfect. There's a small chance of a false positive (an embryo labelled abnormal but is actually normal) or a false negative (an embryo labelled normal but is actually abnormal). The technology is highly accurate, but the inherent limitations of sampling a small number of cells from a rapidly developing embryo mean some uncertainty will always exist.

• Impact on Cumulative Live Birth Rate. For younger patients, while PGT-A might reduce the number of embryo transfers needed to achieve a pregnancy, it may not significantly increase the overall chance of a live birth if all embryos (euploid, aneuploid, and mosaic) were eventually transferred. This is because some aneuploid embryos would naturally not implant or miscarry, and some mosaic embryos could lead to a healthy baby. The benefit here is often about efficiency and reducing emotional distress from failed transfers or miscarriages.

• Disregarding Mosaic Embryos. If all mosaic embryos are discarded without careful consideration, it's possible that a potentially viable pregnancy might be missed, especially for patients with a limited number of embryos.

The ART Act 2021 and PGT-A in India

It's vital for my patients to be aware of the Assisted Reproductive Technology (Regulation) Act, 2021, and its implications for PGT-A in India. The Act has specific provisions regarding genetic testing of embryos, primarily aimed at preventing gender selection. PGT-A is permitted for the diagnosis of genetic diseases and chromosomal abnormalities, but it is strictly prohibited for determining the sex of the embryo. This aligns with ethical medical practices and ensures that genetic technologies are used responsibly for medical rather than non-medical purposes. My clinic strictly adheres to these regulations.

My Perspective: When to Consider PGT-A

As a fertility specialist in Hyderabad, my approach to PGT-A is always individualised. I believe in a thorough, evidence-based discussion with each couple. For those with advanced maternal age, a history of recurrent miscarriages or implantation failures, or previous aneuploid pregnancies, PGT-A is a powerful tool that can significantly improve outcomes and reduce the emotional and financial burden of repeated failed cycles.

However, for younger patients with a good number of embryos and no clear risk factors, I present PGT-A as an option to consider, explaining its potential benefits in reducing time to pregnancy and miscarriage risk, alongside its additional cost and the possibility of discarding viable mosaic embryos. It's never a one-size-fits-all recommendation. The decision must be made collaboratively, weighing the potential benefits against the costs, risks, and personal circumstances.

In practice, my goal is to guide you towards the most effective and compassionate path to parenthood. PGT-A, when applied judiciously, is a significant advancement in reproductive medicine, but it's one piece of a much larger puzzle.

If you are considering IVF and want to understand if PGT-A is right for your unique situation, I encourage you to reach out. I can provide a personalised consultation and discuss all your options in detail.