Adrenal artery velocity waveforms in the appropriate and small-for-gestational-age fetus

The purpose of this study was to compare adrenal artery flow velocity waveforms in the appropriately grown and the small-for-gestational-age fetus. Adrenal artery flow velocity waveforms were prospectively obtained from 131 appropriate- and 21 small-for-gestational-age fetuses with pulsed Doppler ultrasonography. The success rate in recording the adrenal artery was 84% (131/155) and 100% in the appropriate- and small-for-gestational-age fetuses, respectively. The pulsatility index (PI) was used to quantify the waveforms. The PI in the appropriate-for-gestational-age fetuses decreased linearly with gestational age (PI = 1.7-0.016 x gestational age). In ten small-for-gestational-age fetuses the adrenal artery PI was below the 95% confidence interval. Small-for-gestational-age fetuses with abnormal adrenal artery PI had a significantly higher incidence of fetal heart rate decelerations, preterm delivery and Cesarean sections when compared to small-for-gestational-age fetuses with normal adrenal artery PI. Our data indicate that the PI of the adrenal artery in the normal fetus decreases with advancing gestation, and they suggest that in the small-for-gestational-age fetus there is an increased blood flow to the adrenal gland. We postulate that management of the small-for-gestational-age fetus may be aided by the study of the adrenal artery flow velocity waveforms.