Objective: To evaluate the intra- and interobserver reproducibility of three-dimensional power Doppler sonography (3D power Doppler) in the assessment of fetal brain blood flow in the middle cerebral artery territory. Materials and methods: A cross-sectional study was developed with 20 healthy pregnant women between 26 and 34 gestational weeks. The middle cerebral artery territory closest to the transducer was scanned and the blood flow volume was calculated with the method Virtual Organ Computer-aided AnaLysis. The following 3D power Doppler indices were later obtained: vascularization index (VI), flow index (FI) and vascularization-flow index (VFI). The intraclass correlation coefficient (ICC) and Bland-Altman plots were utilized for calculating the intra- and interobserver variability. Results: A good intra- and interobserver agreement was observed, with ICC > 0.90 for all the 3D power Doppler indices: VI [ICC = 0.992 (CI 95%: 0.981–0.997)], FI [ICC = 0.999 (CI 95%: 0.998–0.999)], VFI [ICC = 0.995 (CI 95%: 0.987–0.998)]. Interobserver reproducibility: VI [ICC = 0.988 (CI 95%: 0.970–0.995)], FI [ICC = 0.999 (CI 95%: 0.997– 1.000)], VFI [ICC = 0.994 (CI 95%: 0.994–0.998)]. Conclusion: 3D power Doppler has shown to be a practical and easy method in the assessment of fetal brain blood flow, with good intra- and interobserver reproducibility. The FI presented the best intra- and interobserver agreement.

Keywords: Reproducibility of results; Prenatal ultrasonography; Fetal brain flow; Power Doppler; Threedimensional sonography.