Advanced dynamic Doppler flow of the pulmonary artery in a normal population: reference values from 18 to 41 weeks of gestation calculated by automatic Doppler waveform analysis

The aim of the present cross-sectional prospective study was to establish Doppler reference ranges for blood flow velocity waveforms (V (max), V (mean) and V (min)) and resistance indices (PI, RI) of the fetal pulmonary arteries using the new pulsed-wave color advanced dynamic flow (ADF) Doppler technique. Data were collected in 206 low-risk pregnancies at 18-41 weeks of gestation. The measurements were obtained in the proximal pulmonary artery near the first bifurcation in the absence of fetal body or breathing movements. The pulsatility index (PI) in the pulmonary artery showed mean increases of 2.43-3.59 between gestational weeks 18 and 42. A similar pattern was observed for the resistance index (RI) with increases of 0.79-0.90. Increases in systolic (V (max)), mean (V (mean)) and end diastolic (V (min)) blood flow velocities of 36.0-63.3, 10.8-19.9 and 5.71-7.53 cm/s, respectively, were noted during the observation interval. The ranges for blood flow velocities and impedance indices in the fetal pulmonary artery calculated by the authors may serve as reference values to help distinguish a normal patient population from patients carrying fetuses at high risk for neonatal lung disease in antenatal examinations.