Thesis (M.Sc.) - Cairo University - Faculty of Medicine - Department of Gynecology and Obstetrics

Objective To assess the value of ultrasound use (abdominal and transvaginal) in measurement of the lower uterine segment thickness in women with previous CS, and to determine a cut-off value that can be clinically used to allow a safe vaginal birth after cesarean (VBAC).Methods The lower uterine segment thickness was measured by both transabdominal and transvaginal ultrasound in 200 cases, gravidas (37 week {u2013} 40 week) ,100 cases with previous CS (study group) undergoing repeated CS , and the other 100 cases without any scar in the uterus(control group), then the grade of the scar was assessed intraoperatively.Results We concluded that a best cut-off value was at 3.5mm (using TVS) and this yielded a sensitivity of 63.6% and a specificity of 79.4% at this cut-off value, the positive predictive value was 85.7% while the negative predictive value was 52.9% and the accuracy was 69%. By TAS the best cut- off value was 2.5mm and this yielded a sensitivity of 77.3% and a specificity of 73.5%. At this cut-off value, the positive predictive value was 85% while the negative predictive was 62.5% and the accuracy was 76%.Conclusion Ultrasonographic evaluation permits good assessment of the risk of scar complications intra partum. The lower uterine segment thickness is related to the grade of the scar. The best timing to perform the scan is at late third trimester. A cut-off value of 3.5 mm by TVS, and 2.5 mm by TAS can be safely used with high degree of sensitivity and specificity

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