Response of blood flow velocity waveforms in the abdominal aorta and cotyledonary artery to regional embolization of the umbilical circulation in fetal sheep.

Regional embolization of the placental circulation was performed in 3 anesthetized fetal sheep by retrograde administration of microspheres in a cotyledonary branch of one of the umbilical arteries. Registrations were made of blood velocity waveforms in the fetal abdominal aorta and in a major cotyledonary artery supplying the embolized placental region. Among the fetal lambs examined, a corresponding degree of regression was found between the decrease in umbilical blood flow and increase in the pulsatility index of the abdominal aorta waveforms (coefficient of variation: 0.19). In contrast, the degree of regression between the decrease in umbilical blood flow and increase in the pulsatility index of the cotyledonary artery waveforms varied per fetus (coefficient of variation: 0.79). It is suggested that in human fetuses, in the case of discordant umbilical artery blood flow velocity waveforms, the best information on fetoplacental circulatory competence is provided by the aorta blood velocity waveform.