Value of cervical stiffness measured by trans-vaginal ultrasound and real-time sono-elastography for predicting preterm labor in pregnant women

Abstract

Objective To assess the application value of trans-vaginal ultrasound and real-time sono-elastography in assessing the risk of preterm birth in pregnant women. Methods A total of 108 pregnant women who received prenatal examination at Beijing Obstetrics and Gynecology Hospital from January to November 2017 were included. Based on the presence of threatened premature or preterm labor or not, they were divided into a study group (n=29, with threatened premature or preterm labor) and a control group (n=79, with no threatened premature or preterm labor). Cervical length (CL) was measured by trans-vaginal ultrasound, and the following three cervical elasticity indexes were obtained by sono-elastography: the entire cervical strain rate (CS), the internal cervical os strain rate (IS), and external cervical os strain rate (ES). Independent samples t-test was used to analyze the difference in the above indexes between the two groups. Receiver operating characteristic (ROC) curve analysis was performed to assess the value of the above indexes in predicting the risk of preterm birth. Results CL was significantly lower [(2.94±0.66) cm vs (3.91±0.71) cm] and IS was significantly higher [(0.53±0.28)% vs (0.47±0.20)%] in the study group than in the control group (t=6.436, 3.406, both P 0.05). ROC curve analysis indicated that CL, CS, IS, and ES performed differently in assessing the risk of preterm birth in pregnant women [area under the ROC curve (AUC): 0.156, 0.558, 0.689, 0.499]. The AUCs of CS and IS were greater than 0.50, and the AUC of IS was larger than those of other indexes. Using 0.30% as a cut-off for IS, its sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were 66.7%, 79.3%, 71.1%, 55.4%, and 80.2%, respectively. Conclusions Cervical tissue elasticity indexes obtained by sono-elastography can be used to assess pregnant women at different gestational ages and predict the risk of preterm birth feasibly. IS is more useful than other indexes in predicting early or asymptomatic preterm birth. Key words: Ultrasonography; Elasticity imaging techniques; Cervix uteri; Premature birth