OBJECTIVE: To assess the reproducibility of fetal thigh and upper arm volumes measurement by threedimensional ultrasonography utilizing the eXtended Imaging Virtual Organ Computer-aided AnaLysis (XI VOCAL) method. MATERIALS AND METHODS: This reproducibility study enrolled 43 pregnant women with healthy singleton pregnancies between 20 and 37 gestational weeks. The XI VOCAL 10 planes was the method utilized for volumetric measurement of the fetal limbs. The calculation of the interobserver reproducibility was based on blind volumetric measurements of fetal thighs and upper-arms performed by two observers in 43 fetuses. Intraclass correlation coefficient (ICC), Bland-Altman plots and paired Student's t-test (p) were utilized in the statistical analysis. RESULTS: A high interobserver reproducibility was observed. For the upper arm volume ICC was 0.996 (confidence interval [CI] 95%: 0.992; 0.998) and mean difference = 0.13 ± 1.29% (95% limits of agreement: -2.54; +2.54%). For the thigh volume, ICC was 0.997 (CI 95%: 0.995; 0.999) and mean difference = 0.24 ± 7.60% (95% limits of agreement: -7.6; +7.6%). CONCLUSION: Fetal thigh and upper arm volumes measured by three-dimensional ultrasonography with the XI VOCAL method presented a high interobserver reproducibility.

Keywords: Reproducibility; Fetal limbs volume; Three-dimensional ultrasonography; XI VOCAL.