Transient Elastography to Assess the Cervical Ripening during Pregnancy: A Preliminary Study

Abstract

Purpose To explore the feasibility of transient elastography (TE) to quantify cervical stiffness changes during normal pregnancy and its spatial variability.

Materials and Methods TE was used to quantify the cervical stiffness in four anatomical regions. 42 women between 17 and 43 years of age and at 6 – 41 weeks of gestation were studied. The stiffness was related to gestational age at the time of examination, interval from ultrasound examination to delivery and cervical length to evaluate the potential of TE to assess cervical ripening. In addition, a sensitivity analysis based on Cronbach’s alpha coefficient was carried out to assess the concordance between inter/intra-operator measurements.

Results There were significant correlations between cervical stiffness measured in the four regions with gestational age and the remaining time for delivery. Results confirm stiffness variability within the cervix. No significant association was found between cervical length and stiffness in the four ROIs. Associations between gestational age and remaining time for delivery with cervical length present weaker correlations than with cervical stiffness. The external part of the cervix was significantly softer than the internal one, and these stiffness values vary significantly in the anterior compared to the posterior cervix. The measurements taken by the same and by two different observers for different regions in the cervix were reliable and reproducible.

Conclusion It is feasible to objectively quantify the decrease of cervical stiffness correlated to gestational age. Transient elastography is a valuable promising tool to provide additional information on the process of cervical effacement to that obtained from digital examination and conventional ultrasound. Further studies are needed to assess the feasibility of the technique in obstetric clinical applications, such as prediction of preterm birth or success in labor induction.

Zusammenfassung

Ziel Machbarkeitsprüfung der transienten Elastografie (TE), um räumliche Veränderungen der Zervixsteifkeit (CS) zum Laufe einer Normalschwangerschaft zu erfassen

Material und Methoden Die CS wurde mittels TE in 4 Regionen bei 40 Frauen im Alter von 17 bis 43 Jahren in der 6. – 41. Schwangerschaftswoche bestimmt. Die CS wurde mit dem Gestationsalter zum Untersuchungszeitpunkt, dem Intervall zwischen US-Untersuchung und Entbindung und die Zervixlänge korreliert, um das Potenzial der TE hinsichtlich der Zervixreife zu beurteilen. Danach wurde eine Sensitivitätsanalyse (α-Koeffizienten nach Cronbach) durchgeführt, um die Übereinstimmung der Inter-/Intra-Operator-Messungen zu bestimmen.

Ergebnisse Die CS korrelierte in 4 Regionen mit dem Gestationsalter und der Zeit bis zur Entbindung signifikant. Die Ergebnisse bestätigen die Variabilität der Steifigkeit innerhalb der Zervix. Kein signifikanter Zusammenhang zwischen Zervixlänge und CS in den 4 ROIs. Gestationsalter und Zeit bis zur Entbindung zeigten eine schwächere Korrelation der Zervixlänge als mit der CS. Der äußere Bereich der Zervix war signifikant weicher als der innere Bereich, und diese CS-Werte variierten signifikant in der vorderen Zervix im Vergleich zur hinteren Zervix. Die Intra und Inter-Observervarianz der Messwerte in den 4 Regionen waren zuverlässig und reproduzierbar.

Schlussfolgerung Man kann die sinkende Zervixsteifigkeit im Laufe des Gesationsalters bestimmen. Die TE ist wertvoll und vielversprechend. Sie liefert Zusatzinformationen zur Muttermundöffnung, die über die manuelle Untersuchung und den herkömmlichen US hinaus gehen. Weitere Untersuchungen sind nötig um den Einsatz der TE bei geburtshilflichen Anwendungen, wie Vorhersage von Frühgeburten und erfolgreicher Geburtseinleitung, zu bewerten.

Key words

shear wave elastography - cervix - pregnancy - cervical stiffness

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