Short-term maternal oxygen administration in fetuses with absence or reversal of end-diastolic velocity in umbilical artery: pathophysiological and clinical considerations

Background. The aim of our study was to evaluate the hemodynamic response to acute maternal hyperoxygenation (O-2 test) in a group of growth retarded fetuses with absence or reversal of end-diastolic velocity (AREDV) in the umbilical artery (UA) and to correlate this response to a series of fete-placental velocimetric parameters and clinical variables. Methods. In 25 singleton pregnancies, fete-maternal Doppler velocimetry was performed before and after acute maternal hyperoxygenation. Results. Ten fetuses (40%) exhibited an increase of middle cerebral artery Pulsatility Index (PI) >20% after O-2 (Responders), while in 15 fetuses PI did not change relevantly (Non-responders). Non-responder fetuses showed a higher prevalence of reverse flow in umbilical artery (6/15 vs 0/10; p<0.03) and a slight, but not significant, higher percentage with reversed flow in inferior vena cava (% of A). Also the prevalence of a % of A greater than 95(th) confidence interval was higher in Non-responders (13/15 vs 4/10; p<0.04). Finally the Responder fetuses showed higher peak velocities in the cardiac outflows, even if the difference reached a statistical significance only for the pulmonary artery. The outcome of the two groups did not differ significantly. Conclusions. Our results seem to prove an ability of O-2 test in selecting a group of AREDV fetuses characterized by a higher degree of hemodynamic deterioration and hence 'placed' in a more advanced step of the pathological process leading to overt cardiac decompensation, even if the clinical application of such a test seems to be still of limited value.