Early Postpartum Sonographic Evaluation of Cesarean Scar Following Vaginal Birth after Cesarean Section: a Prospective Cohort Study.

Purpose:To evaluate cesarean scar morphology following vaginal birth after cesarean section (VBAC) and to examine associations of scar parameters with labor and clinical parameters. Materials and Methods:In a prospective cohort study at a single tertiary center, women who had undergone one prior low-transverse cesarean section and delivered vaginally underwent two transvaginal ultrasound examinations: one immediately after delivery and one 24-48 hours postpartum. Scar depth and width, adjacent myometrial thickness (AMT), and residual myometrial thickness (RMT) were measured. Correlations with clinical and labor variables were analyzed. Results:50 women were included. The mean maternal age was 30.7 ± 4.8 years and the mean BMI was 30.3 ± 4.4 kg/m². 41 women completed both examinations. Between the two ultrasound examinations, the mean scar depth and width decreased (15.8 ± 6.7 mm vs. 13.1 ± 4.1 mm; p = 0.009 and 16.8 ± 9.6 mm vs. 12.2 ± 5.8 mm; p = 0.007, respectively), while the AMT and RMT remained unchanged (p > 0.7). Non-spontaneous labor onset was associated with deeper scars (p = 0.027), and spontaneous rupture of membranes correlated with a greater RMT (p = 0.041). Women with a BMI ≥30 kg/m² had a thinner AMT and RMT (p = 0.022 and 0.025, respectively) and more frequent labor augmentation (p = 0.006). No uterine ruptures or major maternal and neonatal complications occurred. Conclusion:Immediate postpartum ultrasound after VBAC elucidated early remodeling of the previous cesarean scar. Non-spontaneous labor onset and a higher BMI were associated with a less favorable scar morphology, though without adverse short-term maternal or neonatal outcomes.