Transabdominal versus transvaginal ultrasound to assess the thickness of lower uterine segment at term in women with previous cesarean section

Abstract

ObjectiveThis study aims to compare transvaginal (TVS) and transabdominal (TAS) ultrasonography precision in to evaluate the lower uterine (LUS) thickness in women with a previous Cesarean section at the term pregnancy; to be an effective method for assessment of previous cesarean scar strength. Material and methodsAn observational cross-sectional study was conducted at kasr el-ainy Hospital in Egypt. From May to November 2020, we admitted 130 pregnant women at term with a previous cesarean section for an elective cesarean delivery. Lower uterine segment thickness was obtained using both transvaginal ultrasound and transabdominal ultrasound before the cesarean. The exact thickness of the lower uterine segment was recorded using a sterile metal ruler before the neonate had been delivered. ResultsThe mean thickness of the lower uterine segment obtained by transabdominal ultrasound was 5.2 ± 1.6 mm and 4.8 ± 1.33 mm by transvaginal ultrasound, then compared each of them to the mean actual thickness, which was 4.5 ± 1.22 mm. The lower uterine segment thickness with transabdominal ultrasound showed a good correlation (r = 0.722) with the actual thickness, the correlation with transvaginal ultrasound was better (r = 0.944). A cut-off value transvaginal ultrasound of 3.65 mm with 90.8% sensitivity and 65.6% specificity. ConclusionTransvaginal ultrasound is more accurate in assessing the thickness of the lower uterine segment than transabdominal ultrasound. A total lower uterine segment thickness of <3.65 is considered a thin scar, and <2.85 mm is associated with a higher risk of uterine dehiscence.The trial was registered in ClinicalTrials.gov registry with clinical trial. https://clinicaltrials.gov/ct2/show/NCT04687891.