Lower uterine segment thickness to predict uterine rupture: a secondary analysis of PRISMA cluster randomized trial
Bibliographic record
Abstract
BACKGROUND: Third-trimester lower uterine segment thickness (LUST) is associated with uterine rupture during trial of labor after cesarean (TOLAC) but threshold values vary according to the approach used (lower values with vaginal ultrasound, higher values with abdominal ultrasound). OBJECTIVE: To estimate the optimal LUST cut-off value combining vaginal and abdominal ultrasound to predict uterine rupture during TOLAC. STUDY DESIGN: We performed a secondary analysis of PRISMA cluster randomized trial including women with a single previous cesarean who underwent ultrasound LUST measurement at 34-38 weeks using the thinnest measurement obtained by combining transvaginal and transabdominal measurements. Participants in the intervention group were informed about the risk of uterine rupture according to LUST reported in 3 categories (≥2.5 mm: low risk-TOLAC is safe; 2.0-2.4 mm: intermediate-risk-TOLAC is safe under specific conditions (e.g., Grobman estimate of vaginal delivery of at or above 70% and/or having a history of vaginal delivery; estimated fetal weight below 4000 grams; interdelivery interval≥18 months); <2.0 mm: high-risk for uterine rupture). Delivery outcomes including uterine rupture were compared using nonparametric analyses and receiver operating characteristics (ROC) curves. RESULTS: Among 3460 participants, 2809 (81%); 385 (11%); and 266 (8%) were identified at low-; intermediate-; and high-risk for uterine rupture, respectively. As expected, low-risk participants were more likely to undergo TOLAC (49% vs 46% vs 13%; P=.001) and more likely to undergo labor induction (16% vs 12% vs 3%, respectively; P=.001) than intermediate-risk and high-risk participants. Four (0.3%) cases of uterine rupture during TOLAC occurred among 1382 low-risk participants but none among the intermediate-risk (0/178) and high-risk (0/35) participants (P=.73). Among low-risk participants, uterine rupture was associated with LUST combining vaginal and abdominal ultrasound (area under the ROC curve: 0.93; 95% confidence interval: 0.86%-0.99%; P=.001) with all cases occuring among women with LUST between 2.5 and 3.0 mm (4/371 or 1.1%) compared to none (0/1011) among those with LUST≥3.0 mm (P=.01). CONCLUSIONS: Third-trimester LUST measurement influences the rates of TOLAC and uterine rupture. TOLAC appears to be associated with a low risk of uterine rupture with a LUST between 2.0 and 2.4 mm under specific conditions. However, these conditions should perhaps be extended to patients with a LUST of less than 3.0 mm, as we found an increase in uterine ruptures in this subgroup (between 2.5 and 3.0 mm) who had no special conditions to comply with. LUST≥3.0 mm combining vaginal and abdominal ultrasound was associated with a very low risk for uterine rupture. A large-scale study using these new parameters would have the potential to demonstrate a reduction in uterine ruptures during TOLAC.
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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 | 0.006 | 0.011 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.009 | 0.008 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.006 |
| Insufficient payload (model declined to judge) | 0.008 | 0.001 |
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".