Are blood flow velocity waveforms related to umbilical cord acid-base status in the human fetus?

Doppler blood flow velocity waveforms from fetal umbilical artery, descending aorta, internal carotid artery and maternal uterine arteries were recorded in 50 fetuses near term undergoing cesarean section before the onset of labor in order to evidence eventual relationships with the fetal acid-base status. The primary indications for cesarean section were in 16 cases an elective repeated cesarean section and in the remaining cases maternal hypertension often associated with fetal growth retardation and/or fetal distress. The technique of anesthesia was strictly standardized and fetal blood gas levels and acid-base status were analyzed in umbilical artery and vein immediately after birth. A significant correlation was found between the pulsatility index from internal carotid artery and the pO2 levels in umbilical vein (r = 0.87; p less than or equal to 0.001). Similar relationships were found between the pulsatility index from descending aorta and the pCO2 (r = 0.78; p less than or equal to 0.001), base excess (r = 0.72; p less than or equal to 0.001) and pH (r = 0.80; p less than or equal to 0.001) levels in umbilical artery. It is suggested that Doppler ultrasound could be useful in the diagnosis of fetal hypoxia and acidosis.