Background and Objectives: The rising rate of caesarean sections worldwide has led to an increasing number of women facing the choice between a trial of labor after caesarean section and elective repeat caesarean delivery. A uterine rupture is the most serious complication of trial of labor after caesarean section and, from a medical point of view, the main reason for an elective repeat caesarean section. Previous studies on the predictive value of lower uterine segment thickness have shown inconsistent results. Conversely, it is unclear what characteristics of the uterotomy site allow for an uncomplicated vaginal birth, even in the presence of defective healing. This study aimed to evaluate the sonographic features of the lower uterine segment in the early postpartum period after successful vaginal birth after caesarean section. Materials and Methods: We conducted a single-center observational cohort study including 30 women after vaginal birth after caesarean section. Transabdominal and transvaginal sonography were performed within the first days postpartum. Measurements included residual myometrial thickness, defect dimensions, and healing ratio after delivery to perform an ex-post analysis with regard to successful vaginal birth. Descriptive statistics were applied. Results: Transabdominal ultrasound (TAS) visualized the uterotomy in 90.0% of patients (27/30), with a median residual myometrial thickness of 12.0 mm (interquartile range 8.0–19.0). Among these, a uterine defect ≥ 2 mm was present in 63.0% (17/27 of visualized cases; 56.7% [17/30] of the entire cohort). Transvaginal ultrasound (TVS) visualized the uterotomy in all patients (29/29), with a median residual myometrial thickness of 9.9 mm (interquartile range 7.5–14.5); a defect was present in 82.8% (24/29 of visualized cases; 80.0% [24/30] of the entire cohort), with a median depth of 9.9 mm (interquartile range 6.5–15.6). Conclusions: Early postpartum sonographic evaluation of the uterotomy scar after vaginal birth after caesarean section frequently reveals even large sonographic uterine wall defects. This study design is not suitable for predicting uncomplicated vaginal delivery, but it demonstrates for the first time—on a retrospective basis—that even large defects in the anterior uterine wall are compatible with an uncomplicated vaginal birth after caesarean section.