Sonographic Lower Uterine Segment Thickness to Predict Cesarean Scar Defect in Term Pregnancy

Abstract

Objective: To study the validity of abdominal sonographic lower uterine segment (LUS) thickness in predicting intraoperative cesarean scar defect (CSD) and thin incision-site uterine wall thickness in term pregnancy. Methods: This was a cross-sectional study involving 111 full-term pregnant women who were scheduled for repeat cesarean delivery from April, 2019 to January, 2020. The abdominal sonographic myometrial LUS thickness was measured prior to surgery. The cesarean scar was assessed using the morphologic classification system as either grade 1 (a normally formed LUS), grade 2 (a thin LUS, but without visible content), or grade 3 (a thin LUS with visible content). Then, the ophthalmic calipers was used to measure the incision-site uterine wall thickness. The correlations between the abdominal sonographic measurements and intraoperative findings were reported. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. Results: There were two cases (1.8%) of grade 3 CSD. The overall correlation between the abdominal sonographic and intraoperative incision-site uterine wall thickness showed r=0.559 with p value < 0.001. The sonographic cut-off value of 1.5 mm could predict CSD and a thin incision-site uterine wall thickness with sensitivity, specificity, PPV, NPV of 50.0%, 90.8%, 9.1%, 99.0%, and 37.5%, 94.6%, 54.5%, 90.0%, respectively. A receiver operating characteristic curve was generated to determine the optimum cut-off value at 2.5 mm with a sensitivity of 76.5% and a specificity of 73.3%. The area under the curve was 0.8 (a 95% confidence interval, 0.718-0.885). Conclusion: Abdominal sonography is a valuable tool for the preoperative predicting of CSD. A myometrial LUS thickness of more than 1.5 mm is associated with a lower likelihood of cesarean scar dehiscence. © 2021, Siriraj Medical Journal. All rights reserved.