Fetal adrenal gland biometry and cervical elastography as predictors of preterm birth: A comparative study

Abstract

Background: Preterm birth is a major health problem in developing and developed countries leading to rising health care costs and long-term neurodevelopmental disability. The study aims to evaluate the role of new quantitative markers, like the elastography of cervix (shear wave speed estimation), fetal adrenal zone enlargement, and corrected fetal adrenal gland volume; in preterm birth prediction and analyze their relative importance. Thus, these markers may be beneficial in early preterm birth detection and prevent the related morbidities.

Methods: Thirty pregnant females (from 28 to 37 weeks of gestational age), showing clinical signs and delivery outcome of preterm birth were included in the study with an equal number of not-in-labor antenatal females at ≥37 weeks as controls. These patients were categorized as preterm and term groups. Both the groups were subjected to trans-abdominal ultrasonography where cervical length, cervical shear wave speed (dynamic elastography) and fetal adrenal gland parameters were measured.

Results: Shear wave speed estimation of the antenatal cervix showed the highest sensitivity and specificity (96.7% and 87% respectively) in the prediction of preterm birth and also showed a strong correlation with fetal adrenal gland enlargement. Fetal adrenal zone enlargement was also shown to be a reliable marker of preterm birth, however, with reduced sensitivity and specificity than shear wave speed.

Conclusion: The elastographic advancement and fetal adrenal biometry derived quantitative markers can be used as an objective and standard criterion for accurate prediction of preterm birth.

Keywords: Preterm birth; adrenal gland; cervix; elastography; tissue elasticity imaging.

Figure 1.

Sono-elastographic images of the cervix on trans abdominal scan in the mid-sagittal plane: (a) measurement of cervical length and (b) elastography using VTQ technique and the rectangular box in the cervix for measurement of shear wave speed (in m/s).

Figure 2.

Sonography of fetal adrenal glands: (a) fetal adrenals (right and left) in trans-axial plane (white arrows); (b) showing fetal zone depth estimation of left adrenal gland in the coronal plane.

Figure 3.

Group scatter plots showing linear correlation of shear wave speed with FZE (a) and cAGV (b) in both preterm and term cohorts. Line of regression was shown with line formula, y = a + bx; R² is regression coefficient.

Figure 4.

ROC curves of different variables in the prediction of timing of delivery/preterm labor: (a) ROC curve of shear wave speed and cervical length; (b) showing curves for fetal zone enlargement (FZE) and corrected adrenal gland volume (cAGV).

Figure 5.

Bland–Altman plots with quadratic regression line of fit (curved dotted line), demonstrating degree of agreement between pairs of FZE (a) and cAGV (b) measurements of both adrenal glands, by the same observer. Mean difference (red line) and ±1.96SD agreement limits (95% confidence interval, dotted green lines) are shown. B = unstandardized coefficient.