Cervical Length and Angle Together Improve Preterm Birth Risk Prediction

Combining transvaginal cervical length and uterocervical angle measurements obtained between 28 and 34 weeks of gestation improves the prediction of preterm birth compared to evaluating either metric on its own, according to a retrospective cohort study published in BMC Pregnancy and Childbirth.

Preterm birth remains a primary cause of neonatal morbidity and mortality across the globe. Although transvaginal cervical length measurement is an established clinical predictor for preterm delivery, its standalone discriminatory capability is limited. The uterocervical angle has been proposed as a supplementary sonographic marker that reflects the biomechanical properties of the cervix and lower uterine segment, but clinical evidence confirming its utility has previously been sparse.

To assess whether evaluating both parameters improves clinical risk stratification, researchers analyzed transvaginal ultrasound scans from 548 pregnancies managed at the University Hospital for Gynecology and Obstetrics Innsbruck between 2013 and 2023. Associations between the imaging metrics and preterm birth were examined through multivariable logistic regression, while overall predictive discrimination was evaluated using receiver operating characteristic curve analysis.

Within the overall cohort of 548 pregnancies, 278 ended in preterm birth, representing 50.7 percent of the patients, while 270 pregnancies delivered at term. The timing of ultrasound evaluation proved crucial to the predictive utility of the measurements. For scans conducted earlier in gestation, specifically between 24 + 0 and 27 + 6 weeks, researchers detected no statistically significant differences in either cervical length or uterocervical angle between pregnancies that delivered preterm and those that reached term.

In contrast, sonographic assessments performed between 28 + 0 and 34 + 0 weeks of gestation revealed pronounced anatomical differences. In pregnancies resulting in preterm birth, transvaginal cervical length was significantly shorter, and the uterocervical angle was significantly wider than in term deliveries. Both markers retained independent statistical associations with preterm birth upon multivariable analysis.

Discriminatory performance assessments demonstrated that cervical length alone provided moderate predictive ability, yielding an area under the receiver operating characteristic curve of 0.614, while the uterocervical angle alone demonstrated weaker discrimination, with an area under the curve of 0.561. Combining both ultrasound measurements enhanced predictive accuracy to an area under the curve of 0.644. Applying optimal cut-off thresholds determined by the Youden index—a cervical length under 15.5 millimeters and a uterocervical angle of at least 101 degrees—the observed proportion of preterm deliveries was highest when patients presented with both sonographic markers simultaneously.

The researchers also evaluated a predefined subgroup of 366 pregnancies that included testing with PartoSure. In multivariable models within this subgroup, a short cervical length maintained an independent association with preterm birth, with an odds ratio of 2.54 (95% confidence interval 1.52 to 4.25, p < 0.001), and a wide uterocervical angle also remained independently associated, showing an odds ratio of 2.10 (95% confidence interval 1.21 to 3.64, p = 0.009). Positive PartoSure results, however, were not independently associated with preterm delivery in the model, demonstrating an odds ratio of 1.66 (95% confidence interval 0.74 to 3.70, p = 0.217). A model combining cervical length, uterocervical angle, and PartoSure achieved the highest numerical discrimination evaluated in this subgroup, yielding an area under the curve of 0.609.

The study authors concluded that transvaginal cervical length and uterocervical angle measured between 28 + 0 and 34 + 0 weeks provide complementary information that aids in risk stratification for preterm delivery. While total discriminatory performance remains moderate, integrating these sonographic markers with PartoSure testing enhances predictive discrimination and can inform clinical management.

Subject of Research: Sonographic prediction of preterm birth using uterocervical angle and cervical length

Article Title: Uterocervical angle and cervical length for prediction of preterm birth: a retrospective cohort study

Article References: Lehmann, M., Sprenger, H., Zheng, Z.-Z., Mohr, L., Emmelheinz, M., Jenewein, K., Steinlechner, M., Tiechl-Egle, J., Alkatout, I., Steger, K., & Azim, S. A. (2026). Uterocervical angle and cervical length for prediction of preterm birth: a retrospective cohort study. BMC Pregnancy and Childbirth. https://doi.org/10.1186/s12884-026-10046-y

Image Credits: AI Generated

DOI: 10.1186/s12884-026-10046-y

Keywords: preterm birth, cervical length, uterocervical angle, transvaginal ultrasound, PartoSure, obstetric risk stratification, Youden index, receiver operating characteristic, area under the curve, multivariable logistic regression, neonatal morbidity, neonatal mortality, lower uterine segment, cervical biomechanics, retrospective cohort study, gestational age