Value of anterior uterocervical angle and cervical length measured by trans-perineum ultrasound in predicting premature delivery

Objective To assess the value of the anterior uterocervical angle (ACA) and cervical length (CL) measured by trans-perineum ultrasound in the prediction of premature delivery. Methods From May 2018 to May 2019, a total of 253 pregnant women at a gestational age of more than 28 weeks who were diagnosed as threatened preterm labor or had high risk factors of preterm labor were selected. According to the pregnancy outcome, the 253 pregnant women were divided into a preterm labor group (54 cases) and a term labor group (199 cases). All pregnant women were examined by trans-perineum ultrasound, and the ACA and CL were measured. The difference in the ACA and CL between the preterm labor group and term labor group was analyzed. Results The average value of the CL in the preterm labor group was (26.18±4.33) mm, which was significantly smaller than that in the term labor group (31.36±3.33) mm (t=8.63, P<0.05). The mean value of the ACA in preterm labor group was significantly higher than that in the term labor group [(117.50±9.61)° vs (102.35±7.59)°, t=-13.428, P<0.05]. In the 253 pregnant women, the area under the receiver operating characteristic (ROC) curve of the CL for predicting preterm delivery was 0.811, and the optimal diagnostic threshold was 25.5 mm; the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 97.0%, 51.9%, 82.3%, 88.1%, and 72.4%, respectively. The area under the ROC curve of the ACA for predicting preterm delivery was 0.921, and the optimal diagnostic threshold was 115.5°; the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 83.3%, 95.5% , 83.3% , 95.4%, and 92.7%, respectively. Conclusion Measuring the ACA and CL by trans-perineum ultrasound has appreciated clinical value in predicting preterm birth, and the ACA is slightly superior to the CL. Since tran-perineum ultrasound is easy to operate and highly repeatable, it is worthy of clinical application. Key words: Premature birth; Perineum; Ultrasonography, prenatal; Anterior uterocervical angle; Cervical length measurement