P-301 Ablation in advance of embryo biopsy or immediately before - implications of two different methods of trophectoderm biopsy for pre-implantation genetic testing
Bibliographic record
Abstract
Abstract Study question Does biopsy method have any impact on the embryo utilisation rate or blastocyst quality? Summary answer Embryo utilisation was not affected by biopsy method. However, without day 3 ablation embryos were better quality overall, and fewer were fully hatched after biopsy. What is known already Trophectoderm (TE) biopsy is currently the most popular technique to remove cells from an embryo for use in pre-implantation genetic testing (PGT). There is currently no standardised method, and various methods currently coexist - although recent studies have found no correlation with biopsy technique and live birth rate after PGT. Other studies have suggested that fully hatched embryos lead to poorer clinical outcomes, which is a particular risk when the zona pellucida must be breached before embryo biopsy. Study design, size, duration This was a retrospective study between 1/10/2022 and 31/12/2024 at Guy’s and St Thomas' Assisted Conception Unit, including 1,028 PGT-M treatment cycles, with 4,068 TE biopsy events. Embryos biopsied between 1/10/2022- 24/11/2023 (Group A) were laser ablated on day 3 and biopsied on day 5/6/7. Embryos biopsied between 25/11/2023 - 31/12/2024 (Group B) were not ablated on day 3; instead collapsed using one laser pulse immediately prior to laser ablation and day 5/6/7 biopsy. Participants/materials, setting, methods ICSI was the fertilisation method for all cycles, and all embryos were cultured in GT-L from day 1 using Embryoscope + (Vitrolife). Laser assisted hatching (RI Saturn laser system, Cooper Surgical) was performed either on day 3 or on the day of biopsy, and embryo biopsy was carried out on day 5,6 or 7 using pulling or flicking as appropriate. Embryos were graded using the Gardner system, and between 5-10 cells were removed from each embryo. Main results and the role of chance Statistical analysis was set at P <0.05. There was no significant statistical difference observed in potential confounding factors between the two groups (age, oocyte number, number of mature oocytes, number normally fertilised (2PN) or number of embryos biopsied). There were no changes in ovarian stimulation protocol, and amplification rate of biopsied cells remained stable throughout the study period. Day of ablation did not affect the number of embryos available to biopsy between Group A and B (45.4% and 45.2% respectively). In Group A, significantly more embryos were biopsied on day 5 compared to day 6 (57.4% vs 38.6%), whereas in Group B the number of embryos biopsied on day 5 and day 6 were similar (48.9% vs 47.5%). However, significantly more embryos biopsied on day 6 in Group A were fully hatched (32% vs < 1% in Group B), and a significantly lower proportion of those embryos were top quality embryos (40% vs 56% in Group B). Top quality embryos were considered those with all A and B grades. In this study, despite the proportion of embryos available to biopsy remaining the same, changing the day of ablation has resulted in fewer hatched embryos and an increase in embryo quality overall. Limitations, reasons for caution This is a single centre, retrospective study which may limit application to other clinics. Further work is needed to correlate the biopsy method with pregnancy and live birth outcomes - since not all embryos biopsied are available for transfer, more time is needed to accumulate this data. Wider implications of the findings The shift in biopsy day and increase in blastocyst quality may mean a lower proportion of embryo mass is removed. This and the reduction of fully hatched embryos may improve clinical outcomes. The even distribution of embryo biopsy across two days has important workflow and staffing implications worth consideration. Trial registration number No
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".