Use of cervical elastography at 18 to 22 weeks' gestation in the prediction of spontaneous preterm birth

Abstract

Background: Accurate identification of the women who will have spontaneous preterm birth continues to be a great challenge. The use of cervical elastography for prediction of preterm birth is promising, but several limitations exist. Newer cervical elastography technology has been developed that may prove useful in evaluation of risk of preterm birth.

Objective: This study aimed to develop standard cervical elastography nomograms for singleton pregnancies at 18 to 22 weeks' gestation using the E-Cervix ultrasound application, assess intraobserver reliability of the E-Cervix elastography parameters, and determine whether these cervical elastography measurements can be used in the prediction of spontaneous preterm birth.

Study design: This was a prospective cohort study of pregnant women undergoing cervical length screening assessment via transvaginal ultrasound examination at 18 to 22 weeks' gestation. A semiautomatic, cervical elastography application (E-Cervix) was used during the transvaginal examination to calculate 5 quantitative parameters (internal os stiffness, external os stiffness, internal -to -external os stiffness ratio, hardness ratio, and elasticity contrast index) and create a standard nomogram for each one of them. The intraobserver reliability was calculated using Shrout-Fleiss reliability. Cervical elastography parameters were compared between those who delivered preterm (<37 weeks) spontaneously and those who delivered full term. A multivariable logistic regression model was performed to determine the ability of the cervical elastography parameters to predict spontaneous preterm birth.

Results: A total of 742 women were included, of which 49 (6.6%) had a spontaneous preterm delivery. A standard nomogram was created for each of the cervical elastography parameters from those who had a full-term birth in the index pregnancy (n=693). Intraobserver reliability was good or excellent (intraclass correlation, 0.757-0.887) for each of the cervical elastography parameters except external os stiffness which was poor (intraclass correlation, 0.441). In univariate analysis, none of the cervical elastography parameters were associated with a statistically significant increased risk of spontaneous preterm birth. In a multivariable model adjusting for history of preterm birth, gravidity, ethnicity, cervical cerclage, and vaginal progesterone use, increasing elasticity contrast index was significantly associated with an increased risk of spontaneous preterm birth (odds ratio, 1.15; 95% confidence interval, 1.02-1.30; P=.02).

Conclusion: Cervical elastography parameters are reliably measured and are stable across 18 to 22 weeks' gestation. Based on our findings, the elasticity contrast index was associated with an increased risk of spontaneous preterm birth and may be a useful parameter for future research.

Keywords: E-cervix; cervical elastography; elasticity contrast index; external os stiffness; hardness ratio; internal os stiffness; spontaneous preterm birth.