Comparison of Pregnancy Outcomes in Ovulatory Frozen Transfer Cycles With or Without Trigger and Non-Ovulatory FET Cycles: A Retrospective Study
Bibliographic record
Abstract
Objective This study aimed to evaluate and compare the pregnancy outcomes in ovulatory frozen embryo transfer (FET) cycles, with or without an ovulation trigger, against non-ovulatory FET cycles. The goal was to identify whether utilizing the natural ovulatory process; either spontaneous or medically induced; yields better clinical outcomes rather than relying entirely on hormone replacement therapy (HRT) for endometrial preparation, focusing on pregnancy rates, ongoing clinical pregnancies, and early pregnancy losses. Design A single centre retrospective cohort analysis. Methods A total of 1490 first-time FET cycles were analyzed. Patients undergoing a first FET cycle with a single vitrified and warmed blastocyst for transfer were stratified based on their FET preparation cycle for comparison. Patients were grouped into non-ovulatory FET cycles (Group A, n=1061), ovulatory FET cycles with ovulation trigger (Group B, n=328), and ovulatory FET cycles without trigger (Group C, n=101). The primary outcomes assessed were pregnancy rates (determined by positive βhCG) and ongoing pregnancy rates (based on detecting a fetal heartbeat at 7 weeks). Secondary outcomes included miscarriage rates. Statistical significance was evaluated using ANOVA and chi-square tests ( P < 0.05). Results Pregnancy rates were comparable between all groups, with 50.3% in Group A, 54.9% in Group B, and 52.5% in Group C ( P = 0.35). Ovulatory cycles (Groups B and C) showed significantly higher ongoing pregnancy rates compared to non-ovulatory cycles ( P = 0.02). The miscarriage rate was higher in Group A (17.0%) compared to Group B (8.9%) and Group C (11.3%), though this difference did not reach statistical significance ( P = 0.07). Conclusions Ovulatory FET cycles, whether triggered or not, result in significantly higher ongoing pregnancy rates and lower miscarriage rates compared to non-ovulatory cycles. These findings support the preservation of the natural ovulatory process, either through spontaneous or induced ovulation, as a key factor in improving clinical outcomes in assisted reproductive technologies (ART). The study highlights the potential advantages of modified natural cycles over artificial cycles that rely solely on exogenous hormone supplementation.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".