- Analysis of over 110,000 UK HFEA treatment episodes: PGT-A associated with lower odds of cumulative live birth
- Miscarriage risk significantly reduced… Highlights the clinical divide between ‘per-transfer success’ and ‘cumulative live birth per oocyte retrieval’
- Observational design and 2014–2018 historical data limitations… “Not a one-size-fits-all tool for every patient”
To couples undergoing In Vitro Fertilization (IVF), few options sound as intuitively reassuring as selecting a “chromosomally normal embryo” for transfer.
Preimplantation Genetic Testing for Aneuploidy (PGT-A) screens embryos for numerical chromosomal abnormalities before intrauterine transfer, allowing clinicians to prioritize euploid embryos. The working assumption seems straightforward: if you screen out aneuploid embryos and transfer only normal ones, shouldn’t the ultimate chance of delivering a baby rise?
However, a large-scale study analyzing national assisted reproductive technology (ART) registry data from the United Kingdom delivered an unexpected answer: while PGT-A significantly reduced the risk of miscarriage, the cumulative live birth rate per egg retrieval cycle was not higher—and was in fact associated with lower odds compared to conventional IVF without genetic testing.
Lower Odds of Live Birth in Both First-Transfer and Cumulative Analyses
Researchers analyzed 111,975 treatment episodes recorded in the UK Human Fertilisation and Embryology Authority (HFEA) registry between 2014 and 2018. In this dataset, a single treatment episode encompasses one oocyte aspiration cycle and all subsequent fresh and frozen transfers utilizing embryos derived from that specific retrieval.
The findings showed that patients undergoing PGT-A had lower odds of delivering a baby compared to those undergoing conventional IVF:
- First Transfer: The adjusted odds ratio (aOR) for live birth was 0.86.
- Cumulative Analysis (All Transfers per Retrieval): The adjusted odds ratio dropped to 0.74.
Even after statistically adjusting for maternal age, infertility etiology, prior IVF attempts, ovarian stimulation protocols, ICSI utilization, oocyte and embryo yield, and clinic-specific effects, PGT-A was not associated with an increased live birth rate.
The most striking clinical disparity lay in the proportion of cycles where no transfer took place:
- In the PGT-A cohort, 48% of patients had no embryo transferred in their initial cycle.
- In the conventional IVF cohort, cycle cancellation without transfer occurred in only 5% of patients.
The investigators noted that when embryos fail to survive biopsy, arrest prior to day 5–6 trophectoderm sampling, or are categorized as untransferable (aneuploid), the pool of available embryos diminishes, directly impacting cumulative delivery outcomes.
Miscarriage Rates Dropped Substantially
PGT-A was not without clear clinical advantages: among patients who achieved a clinical pregnancy, the risk of miscarriage fell substantially in the PGT-A group:
- First-Cycle Miscarriage Odds (per pregnancy): aOR = 0.47
- Cumulative Miscarriage Odds (per pregnancy): aOR = 0.64
This divergence underscores why the PGT-A debate remains intensely polarized:
| Clinical Metric | Conventional IVF | PGT-A Screened Cycles | Clinical Interpretation |
| Embryo Utilization | Higher proportion of embryos transferred | Biopsy and screening filter out abnormal/arrested embryos | Lower cumulative transfer opportunities in PGT-A |
| Cycle Cancellation (No Transfer) | ~5% | ~48% | Higher risk of zero transfer if no euploid blastocyst is identified |
| Miscarriage Risk (per pregnancy) | Baseline | Reduced by 36%–53% | Effective at avoiding early loss from chromosomal aneuploidy |
| Cumulative Live Birth per Retrieval | Reference | Lower odds (aOR 0.74) | Discarding borderline/mosaic embryos or biopsy loss can reduce net baby take-home rate |
PGT-A identifies numerical aneuploidy—the primary cause of early embryonic arrest and first-trimester miscarriage. Selecting a euploid embryo prevents futile transfers and spares patients the emotional and physical trauma of pregnancy loss.
However, “preventing a miscarriage” is not clinically synonymous with “increasing the cumulative probability of taking home a baby from a retrieval.”
This distinction mirrors the UK HFEA’s official “traffic light” rating system for IVF add-ons: PGT-A is rated Red for the explicit goal of “increasing the overall chance of having a baby” in an unselected patient population, but carries a Green rating for reducing miscarriage risk in defined clinical groups. The HFEA notes that because PGT-A acts strictly as a selection filter, it cannot repair an abnormal embryo; it can only reduce the pool of embryos eligible for transfer.
‘Per-Embryo Success’ vs. ‘Per-Retrieval Success’
The central source of confusion surrounding PGT-A lies in the difference between two separate statistical metrics:
- Per-Transfer Success: The likelihood that an individual, biopsied, and confirmed euploid blastocyst will implant and result in a live birth.
- Per-Retrieval (Cumulative) Success: The probability that a patient starting an ovarian stimulation cycle will take home a baby across all transfers originating from that retrieval.
Identifying a high-implantation-potential euploid embryo can significantly shorten time-to-pregnancy (TTP) and eliminate unnecessary transfer cycles.
However, if embryos are excluded due to false-positive test reads, mosaicism classification, or cellular biopsy damage, the patient’s absolute embryo inventory shrinks. For patients with diminished ovarian reserve who produce only one or two blastocysts, losing even one potentially viable embryo can eliminate their entire chance of conceiving from that cycle.
This aligns with guidance from the American Society for Reproductive Medicine (ASRM), which states that routine universal application of PGT-A across all IVF patients lacks evidence of universal clinical benefit. Large-scale randomized trials (such as the STAR trial and ESTEEM) have similarly failed to demonstrate significant superiority in overall live birth rates when PGT-A is applied indiscriminately to all-comer cohorts.
Does This Mean PGT-A Is Unnecessary?
Drawing a blanket conclusion that PGT-A is “useless” or “harmful” would mischaracterize the study’s conclusions:
- Observational Design: This was a retrospective registry analysis rather than a randomized controlled trial. While researchers adjusted for multiple confounders, patients selected for PGT-A in clinical practice often carry poorer baseline prognoses (e.g., recurrent pregnancy loss, prior implantation failure, or advanced maternal age). Statistical adjustments cannot eliminate all residual clinical bias.
- Historical Data (2014–2018): Biopsy techniques, next-generation sequencing (NGS) resolution, and guidelines for managing embryonic mosaicism have advanced considerably since 2018. Critical commentaries published in the same journal emphasized that historical registry datasets may not reflect current laboratory proficiency or modern mosaic reporting standards.
The question is not a binary “should everyone do PGT-A or avoid it?” Rather, it centers on identifying what the patient aims to achieve:
- Patients with High Blastocyst Yield: For patients with multiple blastocysts, PGT-A can efficiently rank embryos, significantly reducing the time and financial cost required to achieve a live birth while minimizing miscarriages.
- Patients with Recurrent Aneuploid Loss: For patients where avoiding another miscarriage is the paramount clinical objective, PGT-A provides meaningful clinical utility.
- Poor Responders with 1–2 Embryos: For patients who produce very few embryos, the risk of biopsy damage, no-result testing, or discarding a viable mosaic embryo may outweigh the benefits of pre-transfer screening.
PGT-A must answer two distinct questions: “Which embryo should be transferred first?” and “Does testing improve this specific patient’s cumulative chance of having a baby?” As this large-scale registry analysis demonstrates, the answers to those two questions do not always align.
Medical Source & Study Reference
- Journal: Reproductive BioMedicine Online (RBMO), Volume 53, Issue 3 (September 2026).
- Study Title: PGT-A is associated with a reduced live birth rate in routine practice: evidence from the UK ART register
- Lead Institutions: University of Manchester; St Mary’s Hospital, Manchester University NHS Foundation Trust, UK.
- Cohort Size: 111,975 treatment episodes from the UK Human Fertilisation and Embryology Authority (HFEA) registry (2014–2018).
- Article Identifiers: Article ID: 105747 | DOI: 10.1016/j.rbmo.2026.105747 | PMID: 42275751
※ This article provides general scientific and medical information and does not replace individualized clinical diagnosis or care. Decisions regarding PGT-A should be tailored to individual patient profiles—incorporating maternal age, reproductive history, previous miscarriages, and oocyte/blastocyst yield—through detailed counseling with an attending reproductive endocrinologist and clinical geneticist.
※ The images associated with this article were generated using generative AI (ChatGPT, OpenAI) as illustrative visual references and do not depict real individuals.
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