Effect of Previous Cesarean Section on Labor Progression: Comparison Between First VBAC and Primiparous Vaginal Deliveries
Bibliographic record
Abstract
Background: The increasing number of cesarean deliveries worldwide has led to a growing population of women eligible for vaginal birth after cesarean (VBAC). limited evidence exists regarding the natural progression of labor among secundiparous women experiencing their first vaginal delivery. Evidence regarding labor progression among women attempting VBAC remains inconclusive and with conflicting results. Clarifying these differences is essential for optimizing intrapartum management. Our objective was to compare the progression rate of the active phase of labor between secundiparous womne at their first VBAC and primiparous women who delivered vaginally. Methods: A retrospective cohort study was conducted at a tertiary university-affiliated medical center (January 2011–January 2021). Included were term singleton pregnancies in spontaneous labor resulting in vaginal delivery. Exclusion criteria included induction, augmentation, and operative vaginal delivery. Results: Among 13,983 primiparous and 736 VBAC patients, the VBAC group was older, used epidural more frequently, and had higher neonatal birth weight. The cervical dilatation rate during the active phase was faster in VBAC patients (3.26 vs. 2.85 cm/h, p = 0.011), with a shorter second stage (77.8 vs. 86.6 min, p < 0.001). The rate of prolonged second stage was higher in the primiparous group (9.5% vs. 7.1%, p = 0.029). In a multivariable analysis examining the association between VBAC and prolonged second stage, VBAC was found to be inversely associated with prolonged second stage (OR 0.541, 95% CI 0.388–0.753, p = 0.001). Conclusions: When compared to primiparous women, women at their first VBAC had significantly shorter active phase and increased progression rate as well as a shorter second stage of labor.
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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 | 0.006 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".