Doppler dynamics: their clinical significance and relationship with fetal blood gases and pH measurements

Abstract

The aim of the study is to demonstrate the ability of abnormal Doppler indices to predict the acid-base status of the fetus. A pulsed Doppler study of umbilical artery, middle cerebral artery and thoracic aorta were assessed on 30 intrauterine growth restricted and 27 appropriate-for-gestational-age fetuses immediately before cordocentesis. All the fetuses with absent end diastolic velocity in the umbilical artery were found to be acidemic by cordocentesis. Thoracic aorta pulsatility index (PI) increased and middle cerebral artery PI decreased significantly with increased umbilical impedance ( r = 0·702, r = -0·340, respectively). Umbilical artery and thoracic aorta PI significantly increased, whereas middle cerebral artery PI decreased with a decrease in umbilical blood pH ( r = -0·760, r = -0·642, r = 0·292, respectively). Doppler findings have a very strong correlation with the acid-base status of the fetuses. Increased umbilical impedance is associated with progressive impairment of placental gas exchange and that by the time diastolic flow is lost hypoxaemia or acidaemia is usually present.