Doppler ultrasonography of the fetoplacental circulation--normal reference values
Pattinson, R.C.; Theron, G.B.; Thompson, M.L.; Lai Tung, M.
South African Medical Journal 76(11): 623-625
1989
ISSN/ISBN: 0256-9574 PMID: 2688142 Document Number: 342257
Normal reference values for the resistance index, A/B ratio and pulsatility index of the umbilical artery obtained by Doppler ultrasonography are presented. The resistance index and A/B ratio values are very similar to those previously published, indicating no need to formulate normal values for different populations. The pulsatility index differed from other published values, probably reflecting different calculation methods built into the spectrum analysers rather than differences in waveforms. The resistance index had the lowest coefficient of variation and showed least inter-observer variation. For routine use the resistance index is preferable to other indices.