Blood flow velocity waveforms from peripheral pulmonary arteries in normally grown and growth-retarded fetuses

The objective of this study was to describe blood flow velocity waveforms of fetal peripheral pulmonary arteries in normally grown and growth-retarded fetuses. Doppler studies were performed in 182 normally grown fetuses (gestational age 18-40 weeks) and in 61 growth-retarded fetuses (gestational age 24-36 weeks) that were free from structural and chromosomal abnormalities and whose umbilical and middle cerebral artery Doppler findings suggested uteroplacental insufficiency as the most likely etiology of the growth defect. The pulsatility index was used to quantify the velocity waveforms. Successful recordings were obtained in 90.1% of the normally grown and 93.4% of the growth-retarded fetuses. In normally grown fetuses the pulsatility index values significantly decreased with advancing gestation. In growth-retarded fetuses the pulsatility index values were significantly elevated compared to those of normal fetuses. A significant relationship was observed between the severity of hypoxia and pulsatility index values from the peripheral pulmonary arteries in 29 fetuses in which Doppler recordings were obtained immediately before cordocentesis. In conclusion, these data show that in normal fetuses the Doppler-measured impedance to flow in the peripheral pulmonary circulation decreases with advancing gestation. Impedance to flow in the lungs is elevated in the presence of growth retardation and this increase is related to the severity of fetal hypoxia.