Doppler study of umbilical artery blood flow waveform. Should we use an instrument-adapted nomogram?

Abstract

Doppler studies of umbilical artery blood flow waveform are becoming an accepted tool of antenatal estimation of fetal well-being. The S/D ratio of the systolic peak (S) to the end-diastolic (D) frequency is the most commonly used parameter. Nomograms relating S/D ratio to gestational age have been published both for normal and pathologic pregnancies. Three hundred twelve analyses of umbilical artery blood flow were performed by continuous Doppler technology in normal, well-dated pregnancies using either one of the following instruments: GE 3600 (GE) or Multigon 500A (MG). Both instruments showed a decrease of S/D with GA, but, by use of a nonpaired t test, a statistically significant difference was found between the two machines. Data on the system used for a particular study should be provided; nomograms for this particular instrument should be consulted and the same machine should be employed for repeat testing in longitudinal studies.