Cervical Strain Elastography in Pregnancy and Association with Maternal Factors

Abstract

Purpose To assess cervical elasticity in different regions by sonoelastography, to compare the results to the Bishop score, cervical length, week of pregnancy and other maternal factors (age, weight, parity) and to evaluate the reproducibility of the method.

Materials and Methods 131 patients between 17 – 41 gestational weeks were examined by transvaginal cervical strain elastography. In the sagittal view strain values were calculated in 7 regions of interest (ROI; external and internal os anterior/posterior, middle part anterior/posterior, cervical canal). In the cross sectional views strain values in 3 ROIs were evaluated at the level of the internal and external cervical os (anterior/posterior, cervical canal). The intra- and interobserver variance was tested.

Results Strain values differed highly significantly in different parts of the cervix (p < 0.001). The anterior parts and the cervical canal were significantly softer with increasing gestational age and Bishop score, and the posterior parts were significantly harder with increasing maternal age, weight, parity. Cervical length showed an inverse relationship to cervical softness. The intra- and interobserver variance was low.

Conclusion Elastography is a reproducible method for the evaluation of cervical elasticity in pregnancy. It showed a significant association with the Bishop score and other maternal factors and could provide additional information about changes in cervical stiffness in pregnancy.

Zusammenfassung

Ziel Ziel der Arbeit war es die Elastizität in verschiedenen Bereichen der Zervix mittels Sonoelastografie zu erfassen und mit dem Bishop Score, der Zervixlänge, Schwangerschaftswoche und anderen mütterlichen Faktoren (Alter, Gewicht, Parität) zu vergleichen, sowie die Reproduzierbarkeit der Methode zu untersuchen.

Material und Methode 131 Patientinnen zwischen 17 – 41 Schwangerschaftswochen wurden mittels transvaginaler Strain-Elastografie untersucht. In der Sagittalebene wurden in 7 Arealen (Regions of interest = ROI) Strain-Werte erfasst (äußerer und innerer Muttermund anterior/posterior, mittlerer Zervixanteil anterior/posterior, Zervikalkanal). In der Querschnittsebene wurden Strain-Werte in jeweils 3 ROIs des äußeren und inneren Muttermunds erfasst (anterior/posterior, Zervikalkanal). Die Intra- and Interobserver Varianz der Methode wurde untersucht.

Ergebnisse Die Strain-Werte unterschieden sich hochsignifikant in den verschiedenen Zervixbereichen (p < 0.001). Die anterioren Teile und der Zervikalkanal waren signifikant weicher mit zunehmendem Gestationsalter und Bishop Score, die posterioren Anteile significant härter mit zunehmendem mütterlichen Alter, Gewicht und Parität. Die Zervixlänge wies eine umgekehrte Relation zur Weichheit der Zervix auf. Intra- and Interobserver Varianz waren gering.

Schlussfolgerungen Die Sonoelastografie ist eine reproduzierbare Methode zur Evaluation der Zervixelastizität in der Schwangerschaft. Es zeigte sich eine signifikante Assoziation zum Bishop Score und anderen mütterlichen Faktoren. Es könnten durch die Elastografie zusätzliche Informationen bezüglich physiologischer Veränderungen in der Zervixelastizität während der Schwangerschaft gewonnen werden, die für die Geburt relevant sind.

Key words

uterus - ultrasound - fetus - elastography - strain - uterine cervix - Bishop score - cervical sonography - prenatal ultrasound

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