Role of Transvaginal Sonographic Measurement of Uterocervical Angle in The Prediction of Preterm Labour

Abstract

Background: Spontaneous pre-term labour (sPTL) remains the leading cause of neonatal morbidity and mortality despite advances in perinatal care. Trans-vaginal sonographic (TVS) cervical length (CL) has modest predictive value. Recent work suggests that the uterocervical angle (UCA)—the angle between the lower uterine segment and the cervical canal—may better capture the vector of intra-uterine force.

Methods: In this prospective observational study we enrolled 100 consecutive women with singleton pregnancies at 16–24 weeks who had ≥ 1 historical risk factor for sPTL (prior sPTB, prior PPROM or mid-trimester loss). After exclusions, 96 women underwent standardized TVS assessment of CL, cervical width (CW) and UCA. Participants were followed until delivery. Primary outcome was birth < 37 weeks. Diagnostic accuracy was assessed with ROC analysis; optimal cut-offs were determined by Youden index.

Results: Twenty women (20.8 %) delivered pre-term. Mean (±SD) UCA was significantly wider in the pre-term versus term group (113.5 ± 17.9° vs 91.6 ± 14.0°, p < 0.001), whereas mean CL did not differ (3.20 ± 0.61 cm vs 3.35 ± 0.55 cm, p = 0.14). An obtuse UCA > 98.5° predicted sPTB with sensitivity 85 %, specificity 79 %, AUC 0.86 and odds ratio 21.3 (95 % CI 6.9-65.0). CW > 3.05 cm was a moderate predictor (AUC 0.74). Combining UCA > 98.5° and CW > 3.05 cm improved sensitivity to 90 % but reduced specificity to 54 %.

Conclusion: In high-risk singleton gestations the mid-trimester UCA outperforms traditional CL screening and, in combination with CW, yields the highest overall sensitivity for sPTB. Routine measurement of UCA at the anatomy scan may enable targeted prophylaxis.