Fetal aortic morphometry by echocardiography: reproducibility study using stringent criteria and standardized nomenclature.

Abstract

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 International Society of Ultrasound in Obstetrics and Gynecology.