Quantitative stress-strain cervical elastography characterizes cervical remodeling in pregnancy

Elastography techniques to date have been limited in their ability to provide repeatable measurements across examiners, preventing the ability to compare within the same patient over time and across patients to define population norms. Innovation to define normal and abnormal biomechanical changes in the cervix during remodeling using methodology that is comparable across large populations of patients would facilitate significant clinical and scientific progress.

The aim of this study was to test the ability of a novel quantitative, synchronized stress-strain cervical elastography system (FQ-CES Fully Quantitative Cervical Elastography System) to numerically quantify cervical remodeling in humans longitudinally over pregnancy and to describe patterns in those with term and preterm birth.

We performed a prospective longitudinal multicenter study of pregnant individuals with singleton gestations from 2021 to 2022 across 3 academic centers in the United States. Participants were enrolled at <16 weeks gestation and had up to 3 quantitative stress-strain cervical elastography exams across pregnancy (11-15 weeks, 18-23 weeks, 28-34 weeks). The device synchronizes quantified pressure applied (stress) and tissue deformation (strain), facilitating direct mathematical calculation of biomechanical cervical softness. Linear mixed effects models were used to describe cervical softening across pregnancy and to compare patterns between preterm and term births. Changes in cervical softness measured with the device were also compared to longitudinal changes in cervical length over pregnancy.

Among 372 patients, 1842 imaging exams across pregnancy were included in this analysis. The device demonstrated statistically significant steady cervical softening as pregnancy progressed (approximately 7.4% softening per week). Nulliparous individuals started pregnancy with 33% harder cervices than multiparous individuals (P<.001). Both starting cervical elastography in early pregnancy and trajectory of cervical softening over pregnancy differed in individuals with preterm birth compared to term birth. People with preterm birth started pregnancy with softer cervixes and exhibited a flatter softening slope, whereas people with term birth outcomes started pregnancy firmer and exhibited a steeper softening slope. Starting cervical length and change in cervical length over pregnancy did not differ in people with term vs preterm birth outcomes.

Cervical elastography using synchronized quantified stress and quantified strain can numerically quantify cervical remodeling patterns longitudinally in human pregnancies that are comparable across populations. This device can detect more robust differences in patients with subsequent preterm birth than cervical length. Use of this device provides a significant technological advancement, opening up a critically important opportunity to advance risk prediction for preterm birth.