Ultrasonic assessment of cesarean section scar to vesicovaginal fold distance: an instrument to estimate pre-labor uterine rupture risk

Background: The number of Cesarean sections (CS) is growing worldwide, intensifying the risk of complications in subsequent pregnancies and leading to increased maternal and fetal morbidity and mortality. In particular, the literature shows a higher risk of uterine rupture (UR) in subsequent pregnancy with trial of labor after cesarean section (TOLAC) Furthermore, there are few data about pre-labor UR in scarred uteri. Objective: Since the key factor for management is timing, the aim of this study was to evaluate the accuracy of prenatal ultrasound (US) of scars in the early determining of pre-labor UR risk in women with a previous CS during their subsequent pregnancy Methods: From April 2014 to November 2018 a retrospective analysis was performed in order to evaluate the scar to vesicovaginal fold (VVF) distance in three patients with pre-labor UR and in 60 cases of the control group. Results: The periconceptional CS scar-VVF distance in the three UR cases resulted significantly increased compared to the controls (23.7 ± 3.5 mm vs 2.3 ± 2.7 mm, p < 005); moreover, a time interval of less than 18 months and a previous pre-labor preterm CS were found as known risk factors. Conclusion: In this study, a higher uterine incision due to placenta previa or isthmic myoma seems to be correlated with a major risk of UR. Therefore, periconceptional US examination of CS-VVF distance, (which represents the level of the previous CS), seems to be a useful predictive factor of pre-labor UR in subsequent pregnancies.