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.
Keywords: Uterocervical angle; cervical length; prematurity; preterm birth; transvaginal ultrasound.