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What Is PGT-A, and Does It Improve IVF Outcomes?

PGT-A tests IVF embryos for chromosome number errors. It may lower miscarriage risk, but for most patients it has not been shown to raise the chance of a birth.

By Vireon Medical Editorial TeamFirst published Evidence checked through

Short answer

PGT-A (preimplantation genetic testing for aneuploidy) checks a few cells from each IVF embryo for an abnormal number of chromosomes, so that only embryos that appear normal are transferred. For most patients it has not been shown to increase the chance of having a baby, and the UK regulator rates it red for that purpose. It can reduce the chance of miscarriage, but it may also leave fewer embryos to transfer, so whether it is worth considering depends on age, the number of embryos and the reason for testing.

Key points

  • PGT-A is an add-on to IVF that requires a biopsy of the embryo.
  • The HFEA rates it red for improving live birth rates in most patients.
  • The HFEA rates it green for reducing miscarriage in most patients.
  • ESHRE does not recommend it for routine clinical use.
  • Results can be wrong, and some healthy embryos may be discarded.

What PGT-A involves

Embryos with missing or extra chromosomes are called aneuploid, and they are less likely to develop into a baby or may result in a genetic condition. PGT-A aims to identify euploid embryos (those with the expected number) and avoid transferring aneuploid ones.1

To do this, embryologists remove cells from the embryo in a biopsy. Testing is now mostly done at the blastocyst stage, on day five or six, when several cells can be taken from the outer layer. The result from those cells is assumed to reflect the whole embryo.1

PGT-A is different from testing for a specific inherited condition that runs in a family. That type of testing has a clear purpose; this page is about screening embryos for chromosome number in general.

Types of study and how Vireon labels evidence Two columns. The left column is a ladder of study designs from generally stronger at the top to generally weaker at the bottom: systematic reviews and meta-analyses of randomised controlled trials; randomised controlled trials; cohort and case-control studies; case series and case reports; and expert opinion or reasoning from first principles. Beneath it, a note says that manufacturer claims are not counted as evidence that a treatment works or is safe. The right column lists the six evidence labels Vireon uses, with their meanings: Strong, consistent high-quality evidence or authoritative guidance supports the claim; Moderate, useful evidence with meaningful limitations; Limited, evidence that is small, non-randomised or otherwise restricted; Mixed, reasonable studies or guidance disagree; Insufficient, the claim has not been established; Uncertain incidence, a risk is plausible or has been reported but how often it happens cannot be reliably calculated. A note across the bottom says that quality within a level also matters, for example a poorly designed randomised trial may rank no higher than a cohort study. Type of study Vireon evidence labels Generally stronger to weaker Systematic reviews and meta-analyses of RCTs Randomised controlled trials (RCTs) Cohort and case-control studies Case series and case reports Expert opinion and reasoning from first principles Manufacturer claims not counted as proof it works or is safe Strong Moderate Limited Mixed Insufficient Uncertain incidence Consistent high-quality evidence or authoritative guidance Useful evidence, with meaningful limitations Small, non-randomised or otherwise restricted evidence Reasonable studies or guidance do not agree The claim has not been established A risk is plausible or reported, but how often it happens is unclear Quality within a level also matters. A poorly designed RCT may rank no higher than a cohort study.
Study design is a rough guide to how much weight a finding can bear, but quality within each level matters too; Vireon’s labels describe the overall evidence behind a specific claim.

Why it might seem to help, and why it often does not

The reasoning is appealing: aneuploid embryos are less likely to lead to a baby, and chromosome abnormalities are linked to miscarriage, so screening them out should help.1 The catch is that PGT-A cannot make an embryo healthier. It can only select among the embryos already created.

In principle, if a person has several embryos, a normal embryo would often have been transferred eventually anyway, so the overall chance of a baby from that egg collection may not change. Meanwhile, the HFEA notes that PGT-A often reduces the number of embryos available for transfer, and that time to a live birth may be longer.1

What the evidence says

A 2020 Cochrane systematic review included 13 randomised trials with 2,794 women.3 For the modern approach (blastocyst biopsy with next-generation sequencing), only one trial of 661 women was available. It was uncertain whether live birth after the first transfer improved, and uncertain whether miscarriage was reduced; no data were available on the cumulative chance of a baby.3

An older technique, FISH (fluorescence in situ hybridisation, which looked at only a few chromosomes), probably reduced live births after the first transfer, and the review authors described it as probably harmful.3 They concluded that the available evidence was insufficient to support PGT-A in routine practice.3

The UK fertility regulator, the HFEA, reached a similar view in 2023. It found no randomised trial evidence that PGT-A improves live birth rates for most IVF patients, but high-quality evidence that it reduces miscarriage, although it does not remove the risk.1 For older women, the HFEA rates the evidence on both outcomes as insufficient.1 The European Society of Human Reproduction and Embryology (ESHRE) states that PGT-A is currently not recommended for routine clinical use.4

OutcomePatient groupHFEA ratingVireon assessment
Live birthMost fertility patientsRed: no evidence of improvement1Insufficient
MiscarriageMost fertility patientsGreen: reduces risk1Moderate
Live birthOlder womenGrey: insufficient evidence1Insufficient
MiscarriageOlder womenGrey: insufficient evidence1Insufficient
HFEA ratings for PGT-A (published October 2023) and Vireon’s reading of the evidence. The Cochrane review rated its own miscarriage finding for modern PGT-A as low certainty, which is why the miscarriage benefit is labelled Moderate rather than Strong.

The HFEA’s colour ratings are based on randomised trials. Red means there is no evidence that an add-on improves live birth rates; green requires more than one good-quality trial showing benefit and safety.2

Possible downsides

There are no known extra physical risks for the person having treatment. The risks fall on the embryos and on decisions made from the results.1

  • Results can be wrong, missing an abnormality or reporting one that is not there.1
  • Some embryos are reported as mosaic (a mix of normal and abnormal cells). These may have a lower chance of pregnancy, but healthy births have been reported, so discarding them may lose a viable embryo.1
  • Removing cells may damage the embryo.1
  • All embryos may be reported as abnormal, leaving none to transfer.1

Common questions

Should PGT-A be offered as standard?

No, according to ESHRE, which does not recommend it for routine clinical use.4 The HFEA advises patients to ask their clinic for the evidence behind any add-on.2

Does a “normal” result mean the pregnancy will be healthy?

No; results can be inaccurate and the test does not remove miscarriage risk.1 Standard pregnancy screening still applies.

Is it more useful if I am older?

It is often marketed that way, but the HFEA rates the evidence for older women as insufficient for both live birth and miscarriage.1 Older patients also tend to have fewer embryos to start with; see how age affects IVF success.

How does PGT-A compare with other add-ons?

Like most add-ons, it lacks strong evidence of improving birth rates; our page on whether IVF add-ons work covers the others.

Bottom line

PGT-A can tell you more about your embryos and may lower miscarriage risk per transfer, but for most people it has not been shown to raise the overall chance of a baby. Anyone considering it should understand the possibility of inaccurate results and of losing embryos that could have led to a pregnancy.

Sources

  1. Human Fertilisation and Embryology Authority. Pre-implantation genetic testing for aneuploidy (PGT-A). HFEA; 2023. https://hfea.gov.uk/treatments/treatment-add-ons/pre-implantation-genetic-testing-for-aneuploidy-pgt-a/. Accessed 5 November 2026.
  2. Human Fertilisation and Embryology Authority. Treatment add-ons with limited evidence. HFEA. https://www.hfea.gov.uk/treatments/treatment-add-ons/. Accessed 5 November 2026.
  3. Cornelisse S, Zagers M, Kostova E, Fleischer K, van Wely M, Mastenbroek S. Preimplantation genetic testing for aneuploidies (abnormal number of chromosomes) in in vitro fertilisation. Cochrane Database of Systematic Reviews; 2020. doi:10.1002/14651858.CD005291.pub3. https://www.cochrane.org/evidence/CD005291_preimplantation-genetic-testing-aneuploidies-abnormal-number-chromosomes-vitro. Accessed 5 November 2026.
  4. ESHRE Add-ons Working Group; Lundin K, et al. Good practice recommendations on add-ons in reproductive medicine. Human Reproduction; 2023. doi:10.1093/humrep/dead184. https://discovery.ucl.ac.uk/10178220/1/dead184.pdf

Article history

  • — First published.