Comparison of color Doppler uterine artery indices in a population at high risk for adverse outcome at 24 weeks' gestation.

OBJECTIVE: To compare uterine artery Doppler velocity and impedance indices in the presence and absence of uterine artery waveform notches, in the prediction of adverse pregnancy outcome in high-risk women. METHODS: One hundred and fifty-seven women identified at Doppler screening as being at 'high risk' underwent a further uterine artery Doppler assessment at 24 weeks' gestation. Pulsatility and resistance indices and minimum, time averaged and time averaged maximum velocities were measured, and the presence of bilateral notches noted. Adverse outcomes were pre-eclampsia, birth weight less than the tenth centile, placental abruption and intrauterine death. The best cut-off for each parameter was assessed by univariate logistic regression, and the comparative performance of the screening parameters was assessed using kappa values. RESULTS: The best performing index in the presence of bilateral notches was mean resistance index, for a cut-off of 0.67, giving a kappa value of 0.65. Mean pulsatility index and lowest pulsatility index performed similarly well, both with kappa values of 0.58. All velocity indices apart from lowest minimum velocity had kappa values of < 0.4. When indices were analyzed, irrespective of notch status, mean resistance and mean pulsatility indices performed similarly, with kappa values of 0.49 and 0.46, respectively; mean minimum velocity had a kappa value of 0.4. CONCLUSIONS: In a high-risk population, uterine artery Doppler mean resistance indices perform better than do velocity indices in the prediction of adverse pregnancy outcome, irrespective of notch status.