Reference values of fetal aortic flow velocity waveforms and associated intra-observer reliability in normal pregnancies
Objectives It was the aim of the present study to calculate new Doppler reference ranges for blood flow velocities (Vmax, Vmean, Vmin) and resistance indices (PI, RI) for the fetal descending aorta by automatic waveform analysis. Design Cross-sectional prospective study. Subjects Nine hundred and twenty-six low-risk pregnancies at 18–41 weeks' gestation. Methods Aortic blood flow velocities were derived with pulsed-wave color Doppler. Measurements were carried out at the level of the diaphragm. Reference ranges for the individual measuring parameters were constructed based on a growth function from a four-parameter class of monotonic continuous functions according to the smallest square pri…