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Summary
Summary
We assessed uterine artery wave form indices according to placental position, and established a method for the objective measurement of the uterine artery waveform notch. Colour Doppler ultrasound was used to image uterine artery flow velocity wave forms from 492 nulliparae between 19 and 24 weeks pregnant. After identification of the placental position, the peak systolic (A), end-diastolic (B), and early diastolic (C) velocities were averaged from four consecutive waveforms. The resistance index was calculated and the wave form notch quantified using the ratio between the systolic peak and the early diastolic velocities (A/C ratio). There was a relationship between the presence of a notch assessed visually and as determined by measurement of A/C ratio. Placental and non-placental side resistance indices and A/C ratio decreased with increasing gestational age. At any gestational age, resistance index and A/C were lower (P > 0–001) on the placental side of the uterus. We concluded that uterine artery wave forms should be analysed according to side and placental position. The A/C ratio is a simple method for quantification of the notch.