Published in:
01-04-2020 | Ultrasound | Original Article–Obstetrics & Gynecology
Reliability and characteristics of ultrasound measurement of fetal umbilical venous blood flow volume according to the site of measurement
Published in: Journal of Medical Ultrasonics | Issue 2/2020
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Purpose
This study aimed at assessing the reliability and characteristics of fetal umbilical venous blood flow volume (UVFV) measurement using ultrasound.
Methods
We conducted a prospective study at our center from November 2017 to July 2019. We performed transabdominal ultrasound examinations at 18–34 weeks’ gestation in uncomplicated singleton pregnancies. UVFV was calculated using vessel diameter (D) and maximum flow velocity (V) as follows: (D/2)2 × π × V × 0.5 × 60 (Q, mL/min). Two examiners measured each value three times in the free-loop (FL) and intra-abdominal (IA) portions of the umbilical vein. Intra-rater and inter-rater reliability was evaluated by intraclass correlation coefficient (ICC) and a Bland–Altman plot.
Results
Two hundred and eight cases were measured by two examiners. The rate of complete measurement at FL and IA was not significantly different (88.5% vs. 79.3%, respectively; p = 0.113). The intra-rater reliability of D and V was high at FL and IA. Regarding inter-rater reliability, the ICC of D, V, and Q was 0.973, 0.582, and 0.963 at FL, and 0.994, 0.912, and 0.989 at IA, respectively. A Bland–Altman plot showed that D and V had greater standard deviation at FL than IA. Regarding Q, the standard deviation at FL was also larger than at IA, and measurement variance at FL increased as the measured value increased, but that at IA did not.
Conclusion
UVFV measurement showed high intra-rater and inter-rater reliability at FL and IA, but the variance of measurements at FL became large as the measured value increased. Properties of different measurement sites should be considered when evaluating UVFV.