Sonographic lower uterine segment thickness after prior cesarean section to predict uterine rupture: A systematic review and meta-analysis

Introduction Cesarean section rates are increasing with a decrease in the rate of trial of labor after cesarean section. The objective of this study was to systematically review the predictive characteristics of sonographic measurement of lower uterine segment thickness for uterine rupture during labor. Material and methods The review was carried out in agreement with PRISMA and SEDATE guidelines. MEDLINE, EMBASE, ClinicalTrials.gov and Cochrane Library were searched from 1990 until November 2018. Quality of included studies was assessed using the QUADAS-2 tool. Data were extracted to construct 2 x 2 tables from each study comparing ultrasound measurement with uterine defect at time of delivery. The data were plotted as a summary receiver-operating characteristic (SROC) curve using the hierarchical SROC model. Results Twenty-eight observational cohort studies met the selection criteria for inclusion. Sonographic lower uterine segment thickness was measured at a gestational age of 36-40 weeks in women with a previous cesarean section. The risk of bias and concerns regarding applicability were low among most studies. The sonographic measurement was correlated with either delivery outcome or lower uterine segment thickness at the time of repeat cesarean section. The cut-off value for lower uterine segment thickness ranged from 1.5 to 4.05 mm across all studies. An association between thin lower uterine segment measurement and uterine dehiscence and uterine rupture was shown in 27 and four studies, respectively. Nineteen studies were included in a meta-analysis with a subgroup analysis by ultrasound methodology. In the subgroup using the ultrasound methodology associated with uterine rupture, the cut-off value is more precise (2.0-3.65 mm) among these 12 studies. There were 18 cases (1.0%) of uterine rupture, 120 (6.6%) of uterine dehiscence and 1674 (92.4%) women with no uterine defect. The SROC curve showed a sensitivity of 0.88 (95% CI 0.83-0.92) and specificity of 0.77 (95% CI 0.70-0.83). The negative likelihood ratio was 0.11 (95% CI 0.08-0.16) and the diagnostic odds ratio was 34.0 (95% CI 18.2-63.5). Conclusions Lower uterine segment thickness >3.65 mm, measured using a standardized ultrasound technique, is associated with a lower likelihood of uterine rupture.