Uterocervical Angle and Cervical Length as a Tool to Predict Preterm Birth in Threatened Preterm Labor

To evaluate the diagnostic performance of uterocervical angle (UCA) and UCA with cervical length (CL) in predicting preterm delivery in threatened preterm labor.

A multicenter prospective observational cohort study was conducted in 160 pregnant women having threatened preterm labor at Srinagarind and Udonthani Hospitals in Thailand between March 2019 and June 2020. Researchers measured UCA and CL by transvaginal ultrasonography. Medical records were reviewed for patient characteristics, and patients were followed up until the date of delivery to assess for the outcome of preterm birth. The cut-off point of UCA was determined from receiver operating characteristic curve analysis. The sensitivity, specificity, likelihood ratio, positive and negative predictive values (PPV and NPV) of UCA and of UCA with CL for predicting preterm birth were determined.

The incidence of preterm birth in women having threatened preterm labor was 27%. The sensitivity, specificity, PPV and NPV of UCA ≥110.97 degrees for predicting preterm birth were 65.1%, 43.6%, 29.8% and 77.3%, respectively. The sensitivity, specificity, PPV and NPV of UCA ≥110.97 degrees with CL <3.4 centimeters for predicting preterm birth were 48.8%, 68.4%, 36.2% and 78.4%. The specificity and NPV of UCA with CL were higher than for UCA alone.

With adequate sensitivity and high NPV, UCA by TVS can be supplemented with CL measurement in threatened preterm labor management to increase the diagnostic performance for predicting preterm birth.