Lower Uterine Segment Thickness Measurement and Uterine Scar Integrity in Pregnant Women with Prior Cesarean Section Using Two-Dimensional Transabdominal Ultrasound

Abstract Background: The number of repeated C.S. is steadily increasing, so the risks are suggested to increase. Measurement of the lower uterine thickness (LUS) close to term is an efficient method for prediction of the scar defect and avoiding uterine rupture. Aim of Study: To determine the normal range of the LUS thickness in pregnant women without prior C.S. near term pregnancy. To evaluate the relationship between the LUS thickness in pregnant women near term with prior one or more C.S. and the occurrence of uterine rupture or scar dehiscence. Patients and Methods: One hundred pregnant women close to term (36 weeks of gestation or more) with prior at least one C. S. (selected cases) and another one hundred women with prior one or more vaginal deliveries (control group) were enrolled in this prospective controlled and follow-up study in Damanhour General Hospital. All the cases were assessed for entire LUS thickness by two dimensional transabdominal ultrasound. The study was carried outduring the period from 6/2020 to 11/2021. The selected cases were followed-up for the scar condition during their deliveries by repeated C.S. After collection of the data in Exile sheets, they were tabulated andstatistically evaluated and analyzed. Results: The LUS thickness for the controlled group was found 4.1±1.0mm. with mode equal 4.0mm, while for the selected group it was found 3.2±0.897mm. with mode equal 3.5mm. The study had showed that the increased time since last C.S. in years is a significantly independent protective factor for scar dehiscence (p=0.038). The cut-off point for LUS thickness as a predictor for scar dehiscence was found <3.6mm (p=0.002) with sensitivity 80% and specificity 51% and 95% confidence interval (CI). Conclusion: Pregnant women with prior C.S. whose LUS thickness was found <3.6mm had to avoid trial for vaginal delivery (VBAC) and to arrange for delivery at shorter gesta-tional age. Recommendations: Are to advise to prolong the time elapsed since the last C.S. as the increased time since last C.S. had been found significantly an independent protective factor for scar dehiscence.