Second Trimester Colour Doppler Imaging of the Uterine Artery: Reproducibility of the Resistance Index

Abstract

Second trimester assessment of uterine blood flow has been advocated as a predictor of subsequent adverse perinatal outcome. The reproducibility of uterine artery resistance index, as assessed using colour Doppler imaging, was investigated. Two observers, both of whom were experienced in colour Doppler assessment of uterine artery flow velocity waveforms, performed the measurements. One-way analysis of variance was used to evaluate intraobserver variability and the limits of agreement method was used to determine the 95% prediction interval for interobserver differences. The intraobserver standard deviation was small for both observers. The limits of agreement for interobserver differences were wide (-0.24, 0.16), similar in magnitude to those reported by other workers who assessed the uterine vessel using continuous wave Doppler. The poor reproducibility of the resistance index suggests that second trimester Doppler assessment of uterine artery flow velocity waveforms may be better described using other semiquantitative methods such as the presence or absence of a diastolic notch.