Uterocervical angle measurement improves prediction of preterm birth in twin gestation

Abstract

Objective An obtuse uterocervical angle (UCA) has been associated with increased risk of preterm birth in singleton gestations. Our objective was to compare the performance of UCA to cervical length (CL) as sonographic predictors of spontaneous preterm birth (sPTB) in patients with twin gestation. Study Design We conducted a retrospective cohort study of twin gestations at a single academic center from May 2008-2016 who received a transvaginal ultrasound for the evaluation of the cervix between 16 0/7 - 22 6/7 weeks. An investigator blinded to clinical outcomes reviewed images of cervical morphology and measured UCA and CL parameters. Data on obstetrical outcomes was extracted from the medical record. The primary outcome was prediction of preterm birth <28 weeks and <32 weeks by UCA and CL. Receiver operator characteristic (ROC) curves and binary logistic regression were used for statistical analysis. Statistical significance was defined as p <0.05. Results Among 259 women with twin gestation, the mean gestational age at birth was 34.83 +/- 3.48 weeks, and 44.7% (n=116) delivered prior to 36 weeks. ROC curves demonstrated optimal prediction of sPTB prior to 32 weeks at a UCA > 110o (80% sensitivity, 82% specificity) vs. CL < 25mm (27% sensitivity, 93% specificity; p<0.001) and similarly, prior to 28 weeks at a UCA>114o (80% sensitivity, 84% specificity) vs. CL< 25mm (35% sensitivity, 90% specificity; p<0.001, Figure). Binary logistic regression revealed UCA > 110o conferred an OR 15.7 (95% CI 7.2-34.4) for delivery prior to 32 weeks, and UCA > 114o an OR 24.3 (95% CI 6.7-88.5) for delivery prior to 28 weeks. In comparison, CL<25mm had an OR 5.2 (95% CI 2.2-12.2) and OR 6.0 (95% CI 2.0-18.1) prior to 32 and 28 weeks respectively. Conclusion Uterocervical angles >110o performed better than the traditional cervical length threshold (25mm) for the prediction of sPTB in a cohort of twin gestations. Measurement of the UCA during the mid-trimester may improve identification of twin gestations at risk for sPTB.