Prospective evaluation of the uterocervical angle as a predictor of spontaneous preterm birth.

INTRODUCTION: The uterocervical angle has been proposed as an ultrasound marker to predict spontaneous preterm birth; however, the studies that provided this evidence were retrospective and their results heterogeneous. This study aimed to assess the ability of the uterocervical angle to predict spontaneous preterm birth before 34 and 37 weeks of gestation. MATERIAL AND METHODS: A prospective cohort study with singleton pregnancies between 19.0 and 22.6 weeks of gestation. Uterocervical angle and cervical length were measured by transvaginal ultrasound. Maternal history and pregnancy data were recorded. Delivery data were subsequently collected. RESULTS: The final analysis included 1453 singleton pregnancies. Spontaneous preterm birth before 37 weeks occurred in 52 cases (3.6%) and before 34 weeks in 17 (1.2%). For the prediction of spontaneous preterm birth before 34 weeks, the area under the curve for the uterocervical angle was 0.67 (95% CI 0.54-0.79) and the detection rates were 5.9% and 23.5% for fixed false-positive rates of 5% and 10%, respectively. For the prediction of spontaneous preterm birth before 37 weeks, the area under the curve was 0.58 (95% CI 0.50-0.67) and the detection rates were 5.8% and 18% for fixed false-positive rates of 5% and 10%, respectively. Combined predictive models were studied. To predict spontaneous preterm birth before 34 weeks, the best model was provided by a combination of uterocervical angle and cervical length (area under the curve 0.72; 95% CI 0.58-0.86). The detection rates of this model were 35.3% and 41.2% for fixed false-positive rates of 5% and 10%, respectively. To predict spontaneous preterm birth before 37 weeks of gestation, the best model was provided by a combination of uterocervical angle, cervical length, and previous history of spontaneous preterm birth (area under the curve 0.64; 95% CI 0.55-0.72). The detection rates of this model were 15.4% and 30.8% for fixed false-positive rates of 5% and 10%, respectively. Obese women and those with a history of cesarean section had a wider uterocervical angle. CONCLUSIONS: The uterocervical angle, measured mid-trimester, is a poor predictor of spontaneous preterm birth.

The uterocervical angle and its relationship with preterm birth.

OBJECTIVES: The objective of this study is to determine whether the uterocervical angle (UCA) correlates with the risk of spontaneous preterm birth (sPTB) < 34 weeks and assess its interobserver variability. STUDY DESIGN: Case-control study of 275 women including 34 who started labor spontaneously and gave birth before 34 weeks of gestation (preterm group) and 241 who gave birth at term (control group). Images used to report cervical length were re-measured for UCA. RESULTS: Mean UCA in the second trimester was wider in the preterm group (105.16°) compared with the control group (94.53°), p = .015. The intraclass correlation coefficient was 0.821 (95% CI: 0.74-0.97) for masked interobserver variability, which implies correct agreement among UCA measurements. Mean UCA increased from the first to the second trimester (84.2° versus 94.5°; p = .019). CONCLUSIONS: Wider UCA in the second trimester is related to sPTB. UCA measurement is a reproducible technique. UCA appears to increase from the first to the second trimester. Prospective studies, with ultrasound examinations aimed at measuring UCA in vivo, are needed to accurately assess the characteristics of this marker and its potential as a predictor of sPTB in clinical practice.