Objective: To assess the utility of cervical funnel volume as a predictor of cerclage failure.
Methods: We performed a retrospective cohort study of pregnant women with a McDonald cerclage and sonographic evidence of cervical funneling between 1/2008 and 2/2014. Funnel volume (FV) was calculated and used as a correction factor for cervical length (CL) or cerclage height (CH). Receiver operating characteristic (ROC) curves were used to compare the predictive value of CL, CL:FV, CH and CH:FV for cerclage failure at <28 or <34 weeks. CL:FV was further stratified to the <5th, <10th and >10th percentiles and analyzed for prediction of preterm delivery.
Results: Subjects with cerclage failure (n = 30) delivered at a mean gestational age of 29.8 +/- 5.3 weeks compared to 38.1+/- 1.39 weeks in those without failure (n = 27; p < 0.001). ROC curves demonstrated CL:FV was the best predictor of delivery <28 weeks (AUC 0.80), while CL was the best predictor of delivery <34 weeks (AUC 0.76). Stratification of CL:FV into <5th versus >10th percentile groups was predictive of early preterm delivery (25.1 weeks versus 34 weeks, p = 0.01).
Conclusions: Volumetric assessment of cervical funneling may improve prediction of cerclage failure in the mid-trimester.
Keywords: Cerclage; cervix; preterm delivery.