Fetal adrenal and middle cerebral artery Doppler velocimetry in high-risk pregnancy

Objectives Animal studies have shown that hypoxic fetuses redistribute their blood flow, giving preferential supply to the brain, heart and adrenal glands. The aim of this study was to establish whether blood velocity wave-forms in the human fetal adrenal artery and middle cerebral artery showed signs of redistribution of fetal circulation in high-risk pregnancy, and to analyze the relationship between signs of such redistribution and the outcome of pregnancy. Methods Fetal middle adrenal artery and middle cerebral artery waveforms were recorded between 27 and 41 weeks of gestation in 102 pregnancies complicated by pregnancy-induced hypertension. Signs of fetal adrenal-sparing were deemed present when the pulsatility index (PI) fell below the fifth percentile of the normal range. Signs of fetal brain-sparing were deemed present when the cerebral artery PI was below the mean -2 SD of the normal range and the cerebroplacental PI ratio was < 1.08. Results Signs of adrenal sparing were found in 64 cases and brain sparing in 32 cases. Fetal adrenal sparing was strongly associated with adverse perinatal outcome; all perinatal mortality cases showed signs of adrenal sparing. There was a significant positive correlation between the fetal adrenal artery PI and umbilical arterial and venous pH. Conclusions Signs of adrenal sparing are frequent in high-risk pregnancies. Adrenal artery velocimetry may be a useful procedure for fetuses at risk for hypoxemia.