O-266 Decoding the clinical fate of segmental mosaic embryos: key predictors of implantation and pregnancy success
Bibliographic record
Abstract
Abstract Study question Does the implantation and pregnancy success of segmental mosaic embryos depend on mosaicism level and aneuploidy type, and can specific chromosomal patterns predict clinical outcomes? Summary answer Higher segmental mosaicism levels reduce implantation and pregnancy rates. Specific chromosomes are linked to implantation failure, underscoring the need for refined embryo selection criteria. What is known already Mosaic embryos can contain normal and abnormal cells due to mitotic errors. Initially classified as aneuploid, they began being transferred after 2015 when no euploid options were available. Segmental mosaics involve partial chromosomal alterations and show better outcomes than whole-chromosome mosaics. PGT-A detects mosaicism, but classification criteria vary. Factors like mosaicism degree and aneuploidy type impact implantation, pregnancy, and live birth rates. Although segmental mosaics are frequently transferred, data remain limited. Current research aims to standardize PGT-A reporting and optimize embryo selection, providing patients with better reproductive options while ensuring safe and effective embryo transfer practices in IVF. Study design, size, duration This retrospective study analyzed 3,790 mosaic embryos from the International Registry of Mosaic Embryo Transfers (IRMET) (2017–2024), classified via PGT-A into segmental mosaics (1,567), whole-chromosome mosaics (1,723), and euploids (19,258). Mosaic embryos were categorized by mosaicism level, aneuploidy type, and morphology. Implantation, pregnancy, and live birth rates were assessed. Standardized sequencing platforms ensured consistency. Statistical models examined correlations between embryo characteristics and outcomes. Participants/materials, setting, methods Data were collected from 20 IVF centers in IRMET. Embryos were classified as segmental mosaic, whole-chromosome mosaic, or euploid via PGT-A. Clinical outcomes were assessed based on mosaicism level, aneuploidy type (deletions vs. duplications), and biopsy timing). Morphological grading (ICM and TE grades) and chromosomal segment size were analyzed. Logistic regression and chi-square tests evaluated statistical significance, ensuring robust conclusions on embryo implantation and pregnancy success. Main results and the role of chance Segmental mosaics had a 45.5% ongoing pregnancy rate (OPR), higher than whole-chromosome mosaics (34.3%) but lower than euploids (50%) (p < 0.005). OPR declined with increasing mosaicism: 50% at 20%, 45% at 30–40%, and 27% at 60%. Single deletions had a 46.3% OPR, outperforming single duplications (41%), with miscarriage rates of 10% and 12%, respectively. Chromosome-specific analyses identified certain chromosomes linked to higher implantation failure. Small deletions (OPR=47%) had better outcomes than large deletions (OPR=43%). Short-arm deletions achieved a 51% OPR, whereas long-arm duplications resulted in a lower OPR (44%). Biopsy timing also influenced outcomes: embryos biopsied on days 4–5 had an OPR of 55%, significantly higher than those biopsied on day 5 (35%) and day 6 (29%) Morphology also played a role, with higher-quality embryos showing better success. These findings highlight the complex interplay of mosaicism, chromosomal patterns, and morphological grading in determining embryo viability. Limitations, reasons for caution Retrospective design and IVF center variability may limit generalizability. While findings suggest key embryo selection factors, prospective studies are needed for validation. Standardizing PGT-A reporting could improve transfer decision-making, ensuring more precise clinical applications and minimizing risks associated with mosaic embryo transfers in reproductive medicine. Wider implications of the findings This study emphasizes the role of mosaicism level, aneuploidy type, and morphology in determining segmental mosaic embryo viability. Standardized PGT-A reporting and refined transfer guidelines could enhance clinical outcomes, allowing for better utilization of mosaic embryos while mitigating implantation risks, thereby optimizing success rates in IVF and assisted reproduction. 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 | 0.001 | 0.000 |
| 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".