To compare the anterior uterocervical angle and cervical length as predictors of spontaneous preterm delivery in patients with transvaginal cerclage.We retrospectively evaluated a cohort of 142 pregnant women with transvaginal cerclage placed over a 5-year period (2010 to 2015) were evaluated. Cervical morphology characteristics were measured from endovaginal imaging, including cervical length, cerclage height, funnel volume and anterior uterocervical angle prior to cerclage placement (UCA 1), shortly after cerclage placement (UCA 2) and the last image prior to delivery (UCA 3). Cerclage failure was defined as delivery prior to 36 weeks. Univariate analysis, receiver operator characteristic curves and binary logistic regression were used for statistical analysis. Statistical significance was defined as a P108o conferred an OR 35.1 (95% CI 7.7 to 160.3) for delivery prior to 34 weeks, and UCA 3>112o an OR 42.0 (95% CI 5.3 to 332.1) for delivery prior to 28 weeks. In comparison, CL<25 mm had an OR 4.7 (95% CI 1.8 to 12.2) for delivery prior to 34 weeks and OR 6.0 (95% CI 1.9 to 19.3) prior to 28 weeks.In patients with transvaginal cerclage, an increasingly obtuse anterior uterocervical angle reflects an increased risk of cerclage failure in the mid-trimester. Utilization of UCA measurement as a surveillance tool may improve identification of patients at risk for cerclage failure.