PGT-A testing (preimplantation genetic testing for aneuploidy) checks IVF embryos for the correct number of chromosomes before transfer, helping to identify which embryos are chromosomally normal (euploid) and which carry an abnormal number of chromosomes (aneuploid). Aneuploidy is one of the leading causes of failed implantation, miscarriage, and certain genetic conditions.
The test involves removing a small number of cells from an embryo at the blastocyst stage (day 5 or 6 of development), sending them for genetic analysis, and using the result to guide which embryo is transferred. It does not change the embryo itself; it simply provides more information.
PGT-A is one of the more widely discussed IVF add-ons, and it is worth understanding both what it can offer and where the evidence is genuinely mixed, so you can have an informed conversation with your consultant. This article explains how PGT-A testing works, who it is typically offered to, what the current evidence shows, and what it costs. If you want to discuss whether PGT-A is relevant to your situation, book a free advisory call with IVF Matters.
What Is PGT-A?
PGT-A stands for preimplantation genetic testing for aneuploidy. The "A" refers to aneuploidy, a condition where a cell has too many or too few chromosomes. A normal human embryo has 46 chromosomes, 23 inherited from each parent. An aneuploid embryo has an incorrect number, which significantly reduces its chance of resulting in a healthy, ongoing pregnancy (Cleveland Clinic, Preimplantation Genetic Testing, 2026).
PGT-A was previously known as preimplantation genetic screening (PGS). It is one of three types of embryo genetic testing used in IVF:
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PGT-A — screens for the correct number of chromosomes (aneuploidy)
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PGT-M — tests for a specific inherited single-gene condition, such as cystic fibrosis or Huntington's disease, when a parent is a known carrier
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PGT-SR — checks for structural chromosomal rearrangements, such as translocations, in embryos where a parent carries a rearranged chromosome
How PGT-A Testing Works
PGT-A testing is only available as part of an IVF or ICSI cycle, since it requires embryos to be created in the laboratory. The process follows several steps:
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Ovarian stimulation and egg collection. Standard IVF stimulation produces multiple eggs, which are collected and fertilised in the laboratory.
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Embryo culture to blastocyst stage. Fertilised eggs are cultured for 5 to 6 days until they reach the blastocyst stage.
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Embryo biopsy. An embryologist removes a small number of cells from the blastocyst's outer layer (the trophectoderm), which will form the placenta rather than the fetus.
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Cryopreservation. The biopsied embryo is frozen while the genetic material is sent for analysis, since results are not available immediately.
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Genetic analysis. The lab assesses the cells for chromosome count using next-generation sequencing. Results typically take 2 to 4 weeks.
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Frozen embryo transfer. A chromosomally normal (euploid) embryo is selected and transferred in a subsequent frozen embryo transfer (FET) cycle.
A 2024 narrative review of preimplantation genetic testing methods notes that trophectoderm biopsy at the blastocyst stage has largely replaced earlier cleavage-stage biopsy, providing more cells for analysis with less apparent impact on embryo development (Fernandes & de Carvalho, Porto Biomedical Journal, 2024).
Mosaic Embryos: An Important Nuance
Some embryos are reported as "mosaic," meaning the biopsied cells show a mix of both normal and abnormal chromosome counts.
Mosaic embryos generally have a lower chance of resulting in a pregnancy than fully euploid embryos, but there are documented cases of healthy live births following their transfer. Because the biopsy samples only a small number of cells, the result may not represent the rest of the embryo, so it is worth asking a clinic directly how they classify and manage mosaic results.
Who Is PGT-A Testing Typically Recommended For?
PGT-A is not routinely recommended for every IVF patient. It is generally discussed with specific groups where the potential benefit is clearer:
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Women of advanced maternal age. Embryo aneuploidy rates rise steeply with age, from approximately 50% under 35 to approximately 80% at age 42.
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Those with recurrent miscarriage. Chromosomal abnormality is a common underlying cause of repeated pregnancy loss.
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Those with previous failed IVF cycles. Where embryos appeared normal under the microscope but implantation repeatedly failed.
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Couples with a family history of chromosomal conditions.
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Cases involving significant sperm chromosomal abnormalities.
At IVF Matters, PGT-A is discussed case by case during the consultation with Dr Irfana Koita, who reviews individual risk factors and treatment history before recommending whether it is likely to be relevant.
What Does the Evidence Actually Show?
The HFEA rates PGT-A as red for improving the overall chance of having a baby for most fertility patients, because it is a selection tool that often reduces the number of embryos available for transfer, and current evidence from randomised controlled trials does not show it improves live birth rates for most IVF patients (HFEA, Treatment Add-Ons: PGT-A, 2023).
At the same time, the HFEA rates PGT-A green for reducing the chance of miscarriage for most fertility patients, based on high-quality evidence, though this does not necessarily translate into an increased chance of having a baby overall, and does not eliminate miscarriage risk entirely.
For older patients specifically, the HFEA currently rates PGT-A as grey (insufficient evidence) for both outcomes in this group, reflecting a genuine research gap rather than a negative finding.
Risks and Limitations of PGT-A
PGT-A does not carry additional medical risk to the patient beyond standard IVF, but there are risks specific to the embryo and testing process:
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Biopsy risk. A small (less than 1%) chance that removing cells could affect the embryo's ability to develop further.
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Misdiagnosis. Although highly accurate (around 98%), a small proportion of results may be inaccurate.
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No embryos suitable for transfer. If all tested embryos come back abnormal, there may be nothing available to transfer that cycle.
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Added time and cost. Testing adds several weeks and increases the cycle's overall cost.
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Mosaic result uncertainty. As discussed above, mosaic results introduce genuine clinical uncertainty.
PGT-A Testing Cost
PGT-A is offered as an add-on to an IVF or ICSI cycle rather than as a standalone treatment, since it requires embryos created through IVF. Costs vary between clinics and typically depend on the number of embryos tested. At IVF Matters, PGT-A pricing is provided as part of a personalised treatment plan; full details are available on the treatment prices page, and you can discuss the cost directly during a consultation based on your specific circumstances.
Frequently Asked Questions
Is PGT-A the Same as NIPT?
No. PGT-A is performed on embryos before transfer, during an IVF cycle, to assess chromosome number prior to implantation. NIPT (non-invasive prenatal testing) is performed during an established pregnancy, using a maternal blood sample, to screen for certain chromosomal conditions in the developing fetus. They serve different purposes at different stages and are not interchangeable.
Can PGT-A Determine the Sex of the Embryo?
Yes, chromosome analysis as part of PGT-A does reveal whether an embryo is chromosomally XX or XY. In the UK, using this information to select an embryo based on sex for non-medical reasons (family balancing) is not permitted under HFEA regulations, except in specific medical circumstances such as avoiding a sex-linked genetic condition.
How Many Embryos Are Typically Needed for PGT-A to Be Worthwhile?
There is no fixed minimum, but PGT-A is generally more useful when you have multiple embryos to choose from, since the test helps select the best embryo for transfer. If only one or two embryos are available, some patients and consultants choose standard morphological assessment rather than adding testing time and cost.
Does a Euploid Result From PGT-A Guarantee a Successful Pregnancy?
No. A euploid result means the embryo has the correct chromosome number, which improves its statistical chance of implanting and developing successfully, but it does not guarantee pregnancy or a healthy baby. Other factors, including uterine receptivity, embryo quality beyond chromosome number, and implantation conditions, also play a role.
Is PGT-A Available on the NHS?
PGT-A is generally not funded by the NHS as part of standard fertility treatment pathways, since it is classified as a treatment add-on rather than a core, proven fertility treatment. Patients wanting PGT-A typically access it through private treatment, where it is offered as an optional addition to an IVF or ICSI cycle.
Take the Next Step
If you are weighing up whether PGT-A testing is relevant to your situation, an honest conversation with a specialist is the best starting point. Book a free advisory call with IVF Matters to discuss your individual circumstances and treatment history.
Resources
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HFEA — Treatment Add-Ons: PGT-A — Official UK regulator evidence rating and safety information for PGT-A
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Cleveland Clinic — Preimplantation Genetic Testing (PGT) — Clinical overview of PGT-A, PGT-M, and PGT-SR
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Fernandes & de Carvalho — Preimplantation Genetic Testing: A Narrative Review — Peer-reviewed review of PGT methods and embryo biopsy techniques, Porto Biomedical Journal, 2024
Explore More
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IVF Matters — Preimplantation Genetic Testing of Embryos (PGT) — PGT-A and PGT-M testing at IVF Matters, including process and eligibility
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IVF Matters — Treatment Prices — Fixed-price packages for IVF, PGT, and all fertility treatments
