Peripheral right pulmonary artery blood flow velocimetry: Doppler sonographic study of normal and abnormal fetuses

The knowledge of fetal lung circulation in normal and abnormal human fetuses is limited. Our objectives were to assess normal values for flow velocity waveforms in the fetal pulmonic circulation and to test the hypothesis that Doppler velocimetry can predict lung hypoplasia. In a cross-sectional study, peripheral right pulmonary artery flow velocimetry was investigated prospectively in 96 healthy fetuses between 14 and 37 weeks' gestation and four fetuses with abnormalities known to induce lung hypoplasia. The pulsatility index was used to quantify the velocity waveforms. In normal fetuses the mean pulsatility index in the peripheral right pulmonary artery was low, being equivalent to that corresponding to 14 to 17 weeks' gestation (2.89; confidence interval = 2.35 to 3.42), increasing at midgestation to 3.44, with a confidence interval of 3.04 to 3.83; P < 0.01. Thereafter, during the late second and third trimesters the mean pulsatility index did not change significantly with GA, being 3.66 (confidence interval = 3.04 to 4.04) at term. In fetuses with proven lung hypoplasia, the pulsatility index measurements were within the 95% confidence limits of those for normal fetuses. In a normal pregnancy, except for the early stages, a relatively stable high vascular resistance of the fetal pulmonary circulation was found. Our preliminary data suggest that the pulsatility index of the lung circulation cannot be used as an indicator of lung hypoplasia.