Fetal aortic morphometry by echocardiography: reproducibility study using stringent criteria and standardized nomenclature.
OBJECTIVE To establish and assess the reproducibility of standardized echocardiographic nomenclature and the protocol for comprehensive evaluation of fetal aortic morphology. METHODS This was a prospective cohort study of fetuses with a normal three-vessel branching pattern of the aortic arch, evaluated from 18-40 weeks' gestation at a single center between January 2024 and November 2024. Alongside standard two-dimensional views, four-dimensional spatiotemporal image correlation cardiac volumes were acquired to establish the correspondence between the longitudinal aortic-arch view and the three-vessel-and-trachea (3VT) view. A comprehensive nomenclature, based on clear anatomical landmarks, and stringent measurement protocol were defined for fetal aortic dimensions and angles measured in the left ventricular outflow tract (LVOT), the longitudinal aortic-arch and the 3VT echocardiographic views. Measurements were performed independently by two observers, with a repeat analysis by a single observer, to assess intra- and interobserver reproducibility, respectively, using intraclass correlation coefficients (ICCs). RESULTS A total of 45 singleton fetuses with normal three-vessel branching were randomly selected to comprise the study population. Parameters measured in the LVOT view demonstrated good-to-excellent intra- and interobserver reproducibility (ICC > 0.8), with excellent reproducibility observed for the sinotubular junction and mid-ascending aorta diameters (except the interobserver reproducibility for mid-ascending aorta diameter (ICC, 0.883 (95% CI, 0.739-0.945)), which was good). Good-to-excellent intra- and interobserver reproducibility (ICC, 0.8-0.9) was also demonstrated for longitudinal aortic-arch diameters and distances between supra-aortic vessels, whereas the ascending-to-descending aorta angle showed moderate intra- and interobserver reproducibility (ICC, 0.652 (95% CI, 0.435-0.798) and 0.593 (95% CI, 0.199-0.776), respectively). In the 3VT view, the standardized aortic diameters and the 3VT angle had good-to-excellent intraobserver reproducibility (ICC, 0.75-0.9). There was also good agreement between the aortic isthmus diameter in the longitudinal aortic-arch view and the 3VT view (ICC, 0.870 (95% CI, 0.458-0.995); P < 0.001). No significant differences or systematic bias were found between observers. CONCLUSION A standardized echocardiographic protocol with uniform nomenclature and anatomical landmarks would enable reliable and reproducible fetal aortic morphometry across multiple echocardiographic views, and would be a significant step towards harmonizing fetal aorta imaging, enabling meaningful comparisons across studies and promoting collaborative research. © 2026 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.