The meaning of various waveform
changesin IUGR
The umbilical arteries have been shown to be gross indicators of fetal circulatory status in general and, by representing the very earliest sign of trouble, are excellentexcluders of fetal hypoxia and or metabolic acidosis whenthey are normal. The literature shows a distinct downturnin outcome when SGA fetuses have abnormal umbilicalartery waveforms. However, many of the
studies in whichumbilical artery waveforms were abnormal had no other
Doppler information and often the very severely compromised fetuses were lumped in with modestly affected ones.
Interestingly, a few years ago
investigators were able to invasively sample the fetal circulation throughpercutaneousumbilical blood sampling methods, and it was found thatincreased end diastolic flow in the MCA correlated withthe PO2 of the fetus and decreased flow during atrial con-
traction in the ductus venosus and
inferior vena cava werecorrelated with the presence of fetal metabolic acidosis.