Comparative Assessment of Uterocervical Angle Using Transvaginal, Transabdominal, and Transperineal Ultrasonography Between 16 and 24 Weeks of Gestation

<b>Objectives:</b> To assess the correlation and agreement of uterocervical angle (UCA) measurements obtained via transabdominal (TAUS), transperineal (TPUS), and transvaginal ultrasound (TVUS) between 16 and 24 weeks of gestation. <b>Methods:</b> In this prospective cross-sectional study, 136 pregnant women underwent UCA and cervical length (CL) assessments using TVUS, TAUS, and TPUS. All measurements were performed by a single experienced operator with an empty bladder. Correlation was assessed using Pearson analysis, while consistency and agreement were evaluated with intraclass correlation coefficient (ICC) and Bland-Altman plots. <b>Results:</b> Mean UCA values differed significantly between modalities (<i>p</i> < 0.001). Moderate correlation (r = 0.547) and consistency (ICC = 0.545) were found between TAUS and TVUS. The Bland-Altman analysis showed a systematic bias of -8° between TAUS and TVUS, with wide limits of agreement (-64° to +32.6°). TPUS showed a higher correlation with TVUS (r = 0.686), but poor consistency (ICC = 0.052), with broader limits of agreement (-32° to +49.2°). <b>Conclusions:</b> Although both TAUS and TPUS showed significant correlation with TVUS for UCA measurement, only TAUS demonstrated moderate consistency, suggesting that it should be used cautiously in clinical practice. TPUS demonstrated considerable variability in individual assessments and does not seem appropriate as a replacement for TVUS. Further studies are needed to validate these findings and improve measurement reliability.