Advanced Preimplantation Genetic Testing for Aneuploidy (PGT-A) to Enhance IVF Success
What exactly is PGT-A testing and how does it fit into fertility treatment?
Key Informations About PGT-A
It screens IVF embryos for chromosome number
46 chromosome euploid embryos has the highest live birth among available embryos
It is not a treatment tool that changes the embryo, but a selection tool identifies the healthy embryos
It can reduce miscarriage risk from chromosome errors
Helps for a healthy and safe live birth
How is the biopsy performed and is it safe for the blastocyst?
The process of PGT-A involves a delicate procedure known as an embryo biopsy. This is typically performed when the embryo reaches the blastocyst stage, which usually occurs on day five or six after fertilisation. At this stage, the embryo has differentiated into two distinct cell types: the inner cell mass (which becomes the fetus) and the trophectoderm (which becomes the placenta). The biopsy carefully removes roughly 5 to 10 cells from the trophectoderm layer, ensuring that the inner cell mass remains untouched and intact.
Safety is a primary concern for any patient. Because the cells are taken from the future placenta and not the fetus itself, the risk of clinically significant damage to the embryo is considered low when performed by experienced laboratories. Once the cells are removed, the embryos are frozen (vitrified) to await the results of the biopsy, while the cell sample is sent to a genetics laboratory for analysis. The modern freezing techniques used today verify that survival rates for these embryos are exceptionally high, maintaining their viability for future transfer cycles.
However, it is important to acknowledge that not every embryo is suitable for biopsy. An embryo must reach the blastocyst stage and be of sufficient quality to withstand the procedure. If an embryo is developing slowly or has poor cellular structure, the embryologist may advise against the biopsy to avoid compromising its potential. Therefore, the number of embryos available for testing depends heavily on the initial response to stimulation and the development of the embryos in culture. This step requires high-precision equipment and skilled practitioners to ensure the embryo remains safe throughout the process.
What does it mean if an embryo is aneuploid or has the wrong number of chromosomes?
Who stands to benefit most from preimplantation genetic testing for aneuploidy?
Groups With Aneuploidy Risk
Advanced maternal age increases aneuploidy rates
For woman over 40, most embryos may be abnormal
PGT-A helps identify normal embryos faster
PGT-A Impoves Outcomes
Recurrent miscarriage patients may benefit
Patients with repeated implantation failures may benefit
Severe male factor infertility may benefit from this testing
Testing may reduce time to pregnancy
How does PGT-A reduce the chances of miscarriage and improve time to pregnancy?
The correlation between chromosomal abnormalities and miscarriage is well-established. By ensuring that only a chromosomally normal embryo is transferred, PGT-A may reduce miscarriage risk, particularly in patients of advanced maternal age or with recurrent pregnancy loss. While it cannot eliminate the risk entirely (as other factors like uterine health and hormonal support play a role), it removes the single largest variable causing early pregnancy loss. For patients who have suffered previous losses, this risk reduction is often the primary motivation for using PGT-A.
Time to pregnancy is a critical metric in fertility treatment. In a standard IVF cycle without testing, a patient might transfer embryos sequentially based on visual grading. If the best-looking embryo is genetically abnormal, the patient undergoes a transfer, waits two weeks for a test, potentially experiences a miscarriage, and then waits weeks or months for the cycle to resolve before trying again. This process can take months. With PGT-A, the abnormal embryos are identified before transfer. The patient goes directly to transferring a euploid embryo, thereby shortening the timeline to a successful pregnancy.
Furthermore, PGT-A supports the practice of elective single embryo transfer (eSET). Because the clinical pregnancy rate per embryo is higher for tested euploid embryos, there is less pressure to transfer two embryos to get a positive result. This leads to safer, singleton pregnancies. The efficiency gained means that fewer transfers are needed to achieve a live birth, which can also have financial benefits by reducing the costs associated with failed transfers and subsequent medical care for miscarriages.
What are mosaic embryos and can they result in a healthy baby?
About Mosaic Embryos
Mixture of both euploid and aneuploid cells
Implemantation rates are lower and miscarriage risk is higher compared to eploid
Considered as a second-tier option when no normal embryos are available
Levels of mosaicism and specific chromosomes involved influence the recommendation
They may have a lower chance of success but they are not non-viable and it is a possible opportunity for patients
Are there specific risks of PGT-A or downsides to the testing process?
How does the HFEA view "add-on" treatments like genetic screening?
HFEA classifies PGT-A as a treatment "add-on"
Add-ons are optional extras beyond routine IVF
PGT-A acknowledges its utility in specific patient groups but may not be beneficial for all
It is efficient, reduces miscarriage and time to pregnancy but not a guarantee
Clinics need to provide transparent information about PGT-A
Patients should discuss suitability with their provider
Why might using PGT-A decrease the chance of having a baby for some patients?
This seems contradictory, but for certain patient groups, using PGT-A may decrease the overall chances of a live birth per cycle started. This is primarily a numbers game. In IVF, some embryos that test as “abnormal” or “mosaic” might have self-corrected or resulted in a healthy birth if transferred. By strictly discarding these, the pool of embryos available shrinks. For a young patient (under 35) with a good prognosis, the natural repair mechanisms of the embryo and the high baseline rate of euploidy might make the testing unnecessary or even detrimental if it leads to discarding a potentially viable embryo due to a false-positive or mosaic result.
Additionally, the stress on the embryo from the culture to the blastocyst stage, the biopsy, and the cryopreservation could, in theory, impact an embryo that is borderline in quality. While robust embryos survive well, fragile ones might not. If a patient produces very few embryos, the risk of cancelling a transfer because all embryos tested are abnormal can be higher than the chance of a transfer working.
Therefore, PGT-A is not a “one size fits all” solution. For younger women with no history of miscarriage, the increase in success rates per transfer might not justify the cost and the risk of reducing the total number of potentially viable embryos. It is a trade-off between the efficiency of the selection process and the cumulative potential of every egg retrieved. This is why personalized medical advice is crucial when deciding on PGT-A testing.
What is the difference between PGT-A, PGT-M, and PGT-SR?
Key Takeaways for Your Fertility Journey
PGT-A (formerly PGS) screens embryos for chromosomal abnormalities to identify those most likely to result in a healthy baby.
The process involves a biopsy of the trophectoderm at the blastocyst stage, meaning the fetus itself is not touched.
Euploid embryos (normal chromosome count) have the highest potential for implantation and the lowest risk of miscarriage.
Aneuploid embryos (abnormal chromosome count) are the leading cause of IVF failure and early pregnancy loss.
This technology is most beneficial for women over 35, those with recurrent pregnancy loss, or those experiencing repeated implantation failure.
Mosaic embryos contain a mix of normal and abnormal cells; some may still result in a healthy pregnancy and require expert counseling.
PGT-A reduces the time to pregnancy and supports single embryo transfer, reducing the risks associated with twins.
Risks include the potential for no results, accidental damage during biopsy (rare), or the discarding of mosaic embryos that might have been viable.
The HFEA classifies PGT-A as an add-on, highlighting the need for careful patient selection rather than universal application.
Using PGT-A does not guarantee a baby,butimproves embryo selection efficiency and may increase pregnancy rates per transfer in appropriately selected patients.
Prof. Dr. Birol Vural
Specialist in Obstetrics, Gynecology, and Reproductive Endocrinology (IVF)
With nearly 30 years of clinical and academic expertise, Prof. Dr. Birol Vural is a distinguished leader in women’s health and reproductive medicine. A graduate of the prestigious Hacettepe University Faculty of Medicine, he is the visionary founder of the Kocaeli University IVF Center. Refining his expertise at world-renowned institutions—including the Sher Institute (New York, USA) and Brussels Free University (Belgium)—Prof. Vural integrates international standards with compassionate, personalized care.
