Cervical strain elastography improves mid-trimester prediction of spontaneous preterm birth beyond cervical length: a...

Spontaneous preterm birth (sPTB) remains a leading cause of neonatal morbidity and mortality, and cervical length (CL) alone has limited predictive performance in asymptomatic women. Cervical strain elastography may capture biomechanical changes that precede cervical shortening. We aimed to evaluate the predictive value of mid-trimester cervical strain elastography parameters, alone and in combination with CL, for sPTB.

In this single-center cohort study with prospectively collected data, 275 singleton pregnancies underwent transvaginal assessment at 18 + 0 to 23 + 6 weeks of gestation. Cervical strain elastography parameters, including hardness ratio (HR), internal os strain (IOS), external os strain (EOS), and the IOS/EOS ratio, were obtained using E-Cervix software, together with CL. The primary outcome was sPTB before 37 weeks. Logistic regression, receiver operating characteristic analysis, pairwise DeLong comparisons, and decision curve analysis were performed to assess predictive performance and clinical utility.

sPTB occurred in 37 of 275 women (13.5%). Among individual predictors, IOS showed the best discrimination for sPTB (AUC 0.797, 95% CI 0.715-0.878), followed by the IOS/EOS ratio (AUC 0.758, 95% CI 0.671-0.846). Among combined models, CL + IOS/EOS achieved the highest overall performance (AUC 0.828, 95% CI 0.771-0.885), with a sensitivity of 73% and a specificity of 82% at the Youden's J optimal cut-off. Pairwise DeLong comparisons showed that CL + IOS/EOS significantly outperformed CL alone and IOS/EOS alone. Decision curve analysis suggested superior net benefit for the combined model across clinically relevant threshold probabilities.

Mid-trimester cervical strain elastography, particularly IOS-related metrics, provides meaningful predictive information for sPTB. Combining elastography with CL improved discrimination and may enhance mid-trimester risk stratification beyond CL alone. External validation is warranted before routine clinical implementation.