The impact of a thin endometrial lining on fresh and frozen–thaw IVF outcomes: an analysis of over 40 000 embryo transfers
Bibliographic record
Abstract
STUDY QUESTION: Does each millimeter decrease in endometrial thickness lead to lower pregnancy and live birth rates in fresh and frozen IVF cycles? SUMMARY ANSWER: Clinical pregnancy and live birth rates decline as the endometrial thickness decreases below 8 mm in fresh IVF-ET and below 7 mm in frozen-thaw embryo transfer (ET) cycles. WHAT IS KNOWN ALREADY: Previous studies have been heterogenous and have shown conflicting results on the impact of endometrial thickness on IVF outcomes. Most studies do not include many patients with an endometrial thickness below 6 mm, and there are few studies of frozen-thaw ET cycles. STUDY DESIGN, SIZE, DURATION: This study is a retrospective cohort analysis of all Canadian IVF fresh and frozen-thaw ET cycles from the CARTR-BORN database for autologous and donor fresh and frozen-thaw IVF-ET cycles from 1 January 2013 to 31 December 2015. A total of 24 363 fresh and 20 114 frozen-thaw IVF-ET cycles were reported during this timeframe. PARTICIPANTS/MATERIALS, SETTING, METHODS: 33 Canadians clinics participated in voluntary reporting of IVF and pregnancy outcomes to the CARTR-BORN database. The impact of endometrial thickness on pregnancy, live birth and pregnancy loss rates were analyzed for fresh IVF-ET and frozen-thaw cycles. MAIN RESULTS AND THE ROLE OF CHANCE: In fresh IVF-ET cycles, clinical pregnancy and live birth rates decreased (P < 0.0001) and pregnancy loss rates increased (P = 0.01) with each millimeter decline in endometrial thickness below 8 mm. Live birth rates were 33.7, 25.5, 24.6 and 18.1% for endometrial thickness ≥8, 7-7.9, 6-6.9 and 5-5.9 mm, respectively. In frozen-thaw ET cycles, clinical pregnancy (P = 0.007) and live birth rates decreased (P = 0.002) with each millimeter decline in endometrial thickness below 7 mm, with no significant difference in pregnancy loss rates. Live birth rates were 28.4, 27.4, 23.7, 15 and 21.2% for endometrial thickness ≥8, 7-7.9, 6-6.9, 5-5.9 and 4-4.9 mm, respectively. The likelihood of achieving an endometrial thickness ≥8 mm decreased with age (89.7, 87.8 and 83.9% in women <35, 35-39 and ≥40, respectively) (P < 0.0001). LIMITATIONS, REASONS FOR CAUTION: This study only included cycles which proceeded to ET, which may overestimate pregnancy outcomes. Approximately 8% of cycles could not be included in the analysis due to data irregularity related to data entry. Demographic data aside from age were unavailable but may be important as lower endometrial thickness may be associated with poor ovarian response. WIDER IMPLICATIONS OF THE FINDINGS: Although pregnancy and live birth rates decrease with endometrial thickness, reasonable outcomes were obtained even with lower endometrial thickness measurements. These data provide valuable guidance for both physicians and patients when confronted with decisions related to a persistently thin endometrium. STUDY FUNDING/COMPETING INTEREST(S): This study was not funded. The authors do not have any conflicts of interests to declare. TRIAL REGISTRATION NUMBER: N/A.
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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 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".