P-175 Do non-expanded blastocysts four hours after thawing predict outcomes in frozen embryo transfers
Bibliographic record
Abstract
Abstract Study question What is the outcome for non-expanded (NE) blastocysts at the time of frozen embryo transfer? Is this affected by cycle preparation (hormone-programmed vs natural cycles)? Summary answer NE blastocysts transferred 4-hours after thawing have lower pregnancy and clinical pregnancy rates than expanded blastocysts. These pregnancy outcomes can be rescued in natural cycles. What is known already Research has shown that the quality of the blastocyst is a crucial factor influencing pregnancy outcomes. The expansion of the blastocyst at the time of frozen embryo transfer (FET) can vary, impacted by its quality and the duration since thawing, a detail that is often omitted from reports. Additionally, there are differences in outcomes between natural cycle FETs and hormone-programmed FETs, though the underlying reasons for these differences remain unclear. Consequently, a thorough evaluation of these factors is essential for refining IVF practices. Study design, size, duration A retrospective cohort analysis was conducted of 458 single blastocyst FET cycles between January 2023 and August 2024 at a single public university affiliated IVF center. At transfer all embryos included in this study were of Gardner’s grade, AA, AB, or BA. Embryos were classified as non-expanded when they had not yet re-expanded to fill the zona pellucida post thaw, and did not have a large cavity. Participants/materials, setting, methods 152 women had NE embryos and 306 controls with full embryo expansion matched for age from the same study period. Patients undergoing PGT-A (preimplantation genetic test) or oocyte donation cycles were excluded. All embryos were vitrified and warmed using Kitazato media and transferred using Wallace catheters with trans-abdominal ultrasound guidance. Data was compared using chi-square or t-tests where appropriate and multivariate logistic regression to control for confounding effects was planned (baseline characteristic with P < 0.10). Main results and the role of chance The analysis demonstrated that the patient characteristics were comparable between the two groups, including antral follicle count (AFC), serum anti-Müllerian hormone (AMH) level, stimulations protocols, gonadotropins dose, ICSI use, oocytes collected, fertilization rate, blastocyst quality and number of frozen blastocysts. The pregnancy rate for NE (46/152, 30.3%) was significantly lower than that of expanded blastocyst(154/306, 50.3%) (p < 0.001). Clinical pregnancy rates differed (NE: 43/152, 28.3% vs. expanded: 126/306, 41.2%, p = 0.006). Miscarriage rates comparing both embryo groups were similar 25.5% vs. 29.4%, (p = 0.74). Comparing protocols with NE, natural cycle FETs exhibited a higher pregnancy rate (20/27, 74.1%) compared to the hormone programed FETs (26/125, 20.8%), (p < 0.001) and subsequently higher clinical pregnancy rates (20/27, 74.1% vs 23/125, 18.4% respectively p < 0.001). When analyzing the expanded blastocyst (all FET types) and NE blastocysts in natural cycles, no statistically significant improvements were found in pregnancy or clinical pregnancy rates (p > 0.05 in both cases) with expanded embryos. Limitations, reasons for caution The retrospective study design may introduce undetected bias. The relatively small number of patients comprising the natural cycle FET group reduces the overall statistical power of this study group Wider implications of the findings Transferring expanded blastocysts four hours after thawing resulted in better clinical outcomes. Natural cycle FETs seem to rescue NE blastocyst potential to some degree, but the underlying mechanism requires further study. Large studies with more natural cycle FETs are needed to verify the reported observations. Trial registration number No
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".