Ultrasound cervical length measurement for prediction of delivery before 32 weeks in women with emergency cerclage for cervical insufficiency

Abstract

Objective To assess the accuracy of ultrasound cervical length for predicting delivery before 32 weeks among women with a threatened second trimester fetal loss treated by emergency cervical cerclage, and to compare it with prediction based on clinically-assessed cervical dilation. Methods Retrospective study (1997–2006) of 70 women with singleton pregnancies who underwent emergency cervical cerclage and ultrasound cervical length measurement between 15 and 26 weeks. The associations between cervical length and delivery before 32 weeks were studied with univariate and multivariate regression. ROC curves were used to determine the most discriminating cut-off value. Results Although ultrasound cervical length measurement was significantly associated with early preterm delivery, its predictive accuracy was moderate with an area under the ROC curve (AUC) of 0.68 (95% CI, 0.54–0.82), which was similar ( P = 0.43) to the AUC of cervical dilation of 0.73 (95% CI, 0.61–0.85). The best cut-off value was 7 mm, corresponding to a doubled risk of delivery before 32 weeks. Its sensitivity was 52%, specificity 82%, PPV 62%, and NPV 76%. It was no more informative than cervical dilation of 3 cm. Conclusion Ultrasound cervical length measurement does not predict early preterm birth better than clinically-assessed cervical dilation in women with an emergency cerclage.