Blood flow velocity in the fetal abdominal aorta and in the umbilical artery in uncomplicated pregnancies.
The blood flow velocity waveform (BFWV) in fetal vessels depends on the stroke volume and the frequency of the fetal heart, the compliance of the vessel and the peripheral resistance of the fetal vascular bed. The objective of the present study was to establish the change of the BFVW throughout gestation and whether the change of the resistance indices are related to the peak flow velocity and/or the end-diastolic flow velocity. The BFVW of the fetal abdominal aorta and of the umbilical artery at 27th-30th week and at 37th-40th week of gestation were analysed in fifteen patients with uncomplicated pregnancies and subsequent normal outcome. The measurement was performed with a pulsed duplex scanner (Kranzbühler). The Doppler beam had a fixed angle of 50 degrees to the fetal vessel in all cases. The peak flow velocity in the fetal aorta remained constant from the 27th-30th week to the 37th-40th week of gestation: 1418 +/- 248 Hz vs. 1448 +/- 269 Hz. The end-diastolic flow, however, showed a significant increase during the respective periods: from 270 +/- 59 Hz to 325 +/- 69 Hz. The peak flow velocity in the umbilical artery was about 25% below that of the fetal aorta: 1028 +/- 149 Hz (27th-30th week) and 1106 +/- 196 Hz (37th-40th week). The end-diastolic flow, however, increased by about 41%: 292 +/- 86 Hz vs. 412 +/- 83 Hz demonstrating a tremendous change of the compliance and the peripheral resistance in the umbilical vascular system. These alterations are also exhibited by the resistance indices. The resistance indices S/D, PI and RI of both vessels were related to the EDF of the abdominal aorta and the umbilical artery at the respective gestational age. It demonstrated that the EDF is of major influence on the calculated resistance indices. The blood flow in the aorta and the umbilical artery was 135(+/- 18) ml/kg/min and 143 (+/- 21) ml/kg/min, respectively. In conclusion, the BFVW for fetal surveillance should be measured under a constant angle in the fetal abdominal aorta. It gives a good information concerning the peripheral resistance and compliance in the respective vascular areas. The EDFV has its lowest value at 200 Hz in the fetal aorta and in the umbilical artery under physiological conditions.
Künzel
W
W
Department of Obstetrics and Gynaecology, University of Giessen, Germany.
Jovanovic
V
V
Grüssner
S
S
Colling
T
T
D001012:Aorta, Abdominal / Q000000981:diagnostic imaging / Q000196:embryology / Q000502:physiology*; D001783:Blood Flow Velocity; D005260:Female; D005318:Fetal Heart / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D016216:Ultrasonography, Prenatal; D014469:Umbilical Arteries / Q000000981:diagnostic imaging / Q000502:physiology*; D014655:Vascular Resistance