Advanced Ultrasound in Diagnosis and Therapy ›› 2018, Vol. 2 ›› Issue (2): 106-112.doi: 10.37015/AUDT.2018.180807

• Original Research • Previous Articles     Next Articles

Assessment of the Cervix Using Strain Elastography in Pregnant Women with Spontaneous Preterm Birth

Jinghua Li, MD, Yuanyuan An, MD, Lina Zhang, MD, Yinghua Xuan, MD, Qingqing Wu, MD*()   

  1. Department of Ultrasound, Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing, China
  • Received:2018-07-01 Online:2018-08-18 Published:2018-08-19
  • Contact: Qingqing Wu, MD,


Objective: Preterm birth is still the leading cause of neonatal mortality. How to identify women who are at a higher risk of preterm birth continues to be one of the main problems in obstetrics. The aim of this study was to estimate the potential value of cervical strain in predicting the risk of preterm birth.
Methods: A total of 152 pregnant women who received prenatal examination in Beijing Obstetrics and Gynecology Hospital during January 2017 and October 2017. On the basis of the clinical diagnostic criteria for preterm birth, all of pregnant women were divided into two groups: There are 50 patients with the diagnosis of threatened premature or preterm labor in the study group and 102 patients without diagnosis of threatened premature or preterm labor in the control group. Measure cervical length by transvaginal ultrasound and obtain three cervical elasticity indexes by strain elastography: Closed internal cervical os strain rate, external cervical os strain rate and midpoint of the cervical canal strain rate. In the study group the pregnant women were divided into three teams: Length of cervix is 2 cm or less (10 cases) for T1, 2 to 3 cm (21 cases) for T2 and 3 cm or more (19 cases) for T3. Independent sample t-test was used to analyze the difference between the two groups. LSD-t test was used in the two groups. The receiver operating characteristic curve was used to analysis these four indicators. Statistical significance was defined as a p value < 0.05.
Results: Cervical length (CL) was lower and cervical os strain rate (CIS) was higher in the study group (2.67 ± 0.76 vs. 3.85 ± 0.65, p < 0.05; 0.53 ± 0.35 vs. 0.27 ± 0.24, p < 0.05). There was a significant difference with CIS in different cervical length team (p = 0.017) and the mean value of CIS in T1 was higher than the last two teams. The cutoff value of CL maximizing the accuracy of diagnosis was 3.2 cm; area under the curves (AUC), sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were 0.877, 73.3%, 87.0%, 82.2%, 73.5%, 86.4% respectively. Combining CL and CIS, the results of AUC, sensitivity, specificity, accuracy, PPV and NPV (0.891, 73.3%, 91.3%, 84.9%, 80.0%, 86.9%) increased in predicting the risk of spontaneous preterm birth, and the cutoff values of the CL and CIS were 3.1 cm and 0.35%.
Conclusion: The shortening of CL and the increasing CIS are closely related to the occurrence of premature birth and can be used as the indexes to predict the preterm labor. CIS can be used as an indicator to monitor early preterm changes. The combination of CL and CIS may have a role in assessing the risk of spontaneous preterm birth.

Key words: Cervix; Length; Strain elastography; Spontaneous preterm birth