Objectives: To assess the intra- and interobserver reliability of the umbilical vein (UV) diameter, time-averaged maximum velocity (TAMX) and umbilical vein blood flow (BF).
Methods: Sixty-three consecutive singleton pregnancies between 24 and 42 weeks were evaluated by two independent operators. UV diameter and TAMX were measured. UV flow was calculated as UV area x 60 x TAMX x 0.5. Reliability analyses were performed by means of the intraclass correlation coefficient (ICC) for agreement. Differences between and within observers were explored and agreement limits calculated by means of the Bland-Altman test.
Results: Satisfactory Doppler parameters were successfully obtained from all fetuses. The intraobserver ICCs for UV diameter, TAMX, and BF were 0.7, 0.59, and 0.55, respectively, whereas the interobserver ICCs were 0.65, 0.46, and 0.60, respectively. The 95% confidence intervals of the intraobserver differences were (+0.15, -0.14), (+8.0, -7.9), and (+150, -138.7), respectively. The 95% confidence intervals of the interobserver differences were (+0.16, -0.16), (+8.5, -8.2), and (+138.8, -141.9), respectively.
Conclusions: Noninvasive Doppler calculation of umbilical vein blood flow and its components are reliable enough for clinical use.