Haemodynamic changes in IUGR fetus with chronic hypoxia evaluated by fetal heart-rate monitoring and Doppler measurement of blood flow velocity.

The measurement of fetal blood flow velocity and 24 h monitoring of fetal heart-rate (FHR) using a computer were performed to clarify the haemodynamics of growth-retarded fetuses with chronic hypoxia. One hundred normal-growth and 18 growth-retarded fetuses were analysed. All the growth-retarded fetuses with chronic hypoxia were characterised by abnormal blood flow velocity waveforms (with the pulsatility index in the descending aorta below the -1.0 SD and in the middle cerebral artery above the +1.0 SD for our reference range, from 100 normal-growth fetuses). In the latter, the incidence of accelerations of defined size and variability in FHR patterns showed a diurnal variation after 30 weeks' gestation. The initial change in FHR patterns during hypoxia in 11 growth-retarded fetuses, resulting in fetal distress, was a derangement of diurnal variations in FHR patterns, followed by a decrease in variability. A rapid increase in blood flow velocity in the middle cerebral artery with the advance of hypoxia was observed before the onset of distress. Maternal low-dose oxygen inhalation elicited a temporary increase in FHR variability in the growth-retarded but not in normal fetuses. Re-inhalation after 1 h elicited a similar change, suggesting that intermittent rather than continuous, oxygen inhalation may be more effective.