Doppler ultrasound is finding an increasing use in perinatal medicine. Unfortunately, its value in clinical practice has yet to be fully established. A more thorough understanding of the Doppler flow velocity waveform in various fetal and placental vessels is required before adapting this technology into clinical decision making processes. The studies involved in this thesis were designed with the following aims: 1. To perform calibration studies on the equipment used to investigate the fetal and uteroplacental circulations. 2. To establish normal values throughout normal human gestation for the fetal aorta, inferior vena cava, umbilical artery and the maternal uteroplacental artery. 3. To study the variability of Doppler recordings at different sites of the umbilical artery and fetal aorta. 4. To examine the possibility of investigating ovine pregnancy using Doppler ultrasound and to compare the gestational age influences on the flow velocity waveform with those seen in the human pregnancy. 5. To investigate pregnancies complicated by hypertension with Doppler ultrasound in order to determine the value of this technique in detecting signs of fetal compromise before the standard tests of assessing fetal well being. 6. To investigate derangements of the fetal heart seen in human pregnancy with Doppler ultrasound and to prepare a guide for clinicians managing such problems. 7. To create an animal model of fetal hydrops using atrial pacing and to investigate the development of the condition using Doppler ultrasound. (Abstract shortened by ProQuest.)
