Cervical consistency index and quantitative cervical texture analysis by ultrasound to predict spontaneous preterm birth

Abstract

INTRODUCTION: Preterm birth (PTB) remains a major contributor to perinatal morbidity and mortality being the second leading cause of death in children under 5 years of age. The rate of spontaneous preterm birth (sPTB) still accounts for approximately 5%-12% in USA and in most developing countries. Cervical length (CL) <25 mm measured with transvaginal ultrasound at mid-gestation is a known risk factor for sPTB. However, its value for screening a whole pregnant population consisting mainly of women without risk factors for sPTB remains controversial because of the low sensitivity of short CL in low-risk women. MAIN OBJECTIVE: To improve the identification of women at increased risk of sPTB in low and high sPTB risk asymptomatic pregnancies during mid-gestation with two innovative transvaginal ultrasound techniques, the Cervical Consistency Index (CCI) and the Quantitative Cervical Texture Analysis (CTx). The CCI is an ultrasound measurement that aims to estimate cervical softness by measuring maximal tissue compressibility with a vaginal ultrasound probe. The CTx, extracts information from the speckle pattern of the ultrasound image and identifies the patterns associated with SPTB.

METHODS: Articles 1 and 2 are prospective cohort studies that compare the predictive capacity of the ICC with that of the CL. Article 3 is a cross-sectional study that analyzes the cervical texture along a term gestation. Article 4 is a case-control study, in which a CTx-score is obtained, which is compared with the CL.

RESULTS: STUDY 1. Mid-trimester sonographic cervical consistency index to predict spontaneous preterm birth in a low-risk population: The cervix was significantly shorter (median CL 39.8 mm vs. 36.2 mm, p=0.004) and the CCI was significantly lower (median 73.0% vs. 58.1%, p<0.001) in the sPTB group. The area under the ROC curve (AUC) for CCI with regard to predicting sPTB <37+0 weeks was 0.84 (95% CI 0.75-0.93) and that for CL 0.68 (95% CI 0.56-0.81), P = 0.03. STUDY 2. Mid-trimester sonographic cervical consistency index to predict spontaneous preterm birth in a high-risk population: The CCI (%) was significantly inferior in women who had a preterm delivery compared to the term group. CCI adjusted OR, 0.91 (95% CI, 0.83-0.99; P=0.03). The AUC of the CCI to predict sPTB <37+0 weeks was 0.73 (95% CI, 0.61-0.85) while that of CL was 0.51 (95% CI, 0.35-0.67), P=0.03. STUDY 3. Quantitative Analysis of the Cervical Texture by Ultrasound and Correlation with Gestational Age: The correlation between the gestational age at which the images were obtained and the estimated gestational age by quantitative analysis of the cervical texture was R=0.88. Ce STUDY 4. Quantitative analysis of the cervical texture by ultrasound in the mid-pregnancy is associated with spontaneous preterm birth: The median CTx-based score obtained was significantly lower in cases compared to controls. The CTx-based crude OR 0.31 (95% CI 0.17-0.56; P<0.001) vs. adjusted OR 0.37 (95% CI 0.19-0.64; P=0.001). The AUC for the CTx-based score to identify women delivering < 37+0 weeks was higher (0.77; 95% CI 0.66-0.87) than for CL (0.60; 95% CI 0.47-0.72), P=0.02. DISCUSSION: The CCI and CTx have the potential to improve the identification of women at increased risk of sPTB compared to CL. The large number of scenarios in which these tools could be applied have demonstrated their potential impact on the current management of a large number of pregnancies. Cervical assessment is required in a wide range of clinical situations and the main reason why it is not yet universally implemented is the limited performance of the current cervical assessment techniques. Therefore, it is a healthcare priority to develop sPTB predictive tools with sufficiently improved performance to be used as screening tools.

INTRODUCCIÓN: El parto prematuro representa la segunda causa de morbimortalidad infantil a nivel mundial. Las estrategias actuales de detección de las mujeres con un riesgo aumentado de parto prematuro espontáneo (SPTB), han demostrado ser insuficientes y el desarrollo de nuevas herramientas predictivas es una prioridad en el campo de la medicina materno-fetal.

OBJETIVOS: Mejorar la identificación de las mujeres con riesgo de SPTB en el segundo trimestre, evaluando dos nuevas herramientas ecográficas: el Índice de Consistencia Cervical (CCI) y el análisis cuantitativo de la textura cervical (CTx).

MÉTODOS: El CCI, evalúa la máxima compresibilidad del cuello del útero. El CTx, extrae información del patrón de moteado de la imagen ecográfica e identifica los patrones asociados con SPTB. Los artículos 1 y 2, son estudios prospectivos de cohortes que comparan la capacidad predictiva del CCI con la de la CL. El artículo 3 es un estudio transversal que analiza la textura cervical a lo largo de una gestación a término. El artículo 4 es un estudio de casos y controles, en el cual se obtiene un CTx-score, que se compara con la CL.

RESULTADOS: Las curvas ROC para la predicción de SPTB <37 y <34 semanas del CCI (0.84 y 0.73), son significativamente mejores que las de la CL (0.68 y 0.51). El CTx-score en los casos de SPTB es significativamente inferior que en los controles. La curva ROC del CTx-score es mejor en comparación con la de la CL (0.77 vs 0.60).

CONCLUSIONES: Los artículos 1 y 2, demuestran que el CCI es mejor predictor de SPTB que la CL en poblaciones de bajo y alto riesgo de prematuridad. El artículo 3 demuestra que la CTx puede identificar cambios a lo largo de la gestación normal. El artículo 4 demuestra que el CTx-score obtenido en casos y controles, se relaciona con el SPTB.