Doppler studies on the fetal renal artery in the severely growth-restricted fetus

To examine changes with time in the fetal renal circulation by Doppler sonography in the severely growth-restricted preterm fetus during the period of gradual deterioration prior to delivery, and to examine the relationship between Doppler measurements, amniotic fluid index, birth weight and fetal condition at birth.

This was a prospective observational study in 16 preterm growth-restricted fetuses between 26 and 35 weeks of gestational age. Serial Doppler measurements were made of the renal artery, umbilical artery, middle cerebral artery and ductus venosus.

The pulsatility index in the renal artery did not show any correlation with cord blood pH, birth weight or amniotic fluid index corrected for gestational age (Delta/SDAFI). However, peak systolic velocities in the renal artery showed a significant reduction with time (n = 7, P < 0.05) and a significant correlation with: venous cord pH at delivery (n = 12, r = 0.84, P < 0.001), Delta/SDAFI (n = 16, r = 0.67, P < 0.01), and birth weight (n = 16, r = 0.61, P < 0.02). Birth weight correlated significantly with: Delta/SDAFI (n = 15, r = 0.57, P < 0.05), pulsatility index values of the middle cerebral artery (n = 15, r = -0.61, P < 0.02), and pulsatility index values of the ductus venosus (n = 16, r = 0.55, P < 0.05), and Delta/SDAFI correlated significantly with: pulsatility index values of the ductus venosus (n = 15, r = 0.51, P < 0.05) and arterial cord pH values at delivery (n = 8, r = 0.78, P < 0.05).

Progressive redistribution of the circulation occurs with deterioration of the fetal condition in the growth-restricted preterm fetus. On spectral Doppler this is reflected by changes in peak systolic velocities, but not by changes in pulsatility values of the fetal renal artery waveforms.