Effect of Previous Cesarean Section on Labor Progression: Comparison Between First VBAC and Primiparous Vaginal...

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.