Blood flow velocity waveforms of the fetal middle cerebral artery in a normal population: reference values from 18 weeks to 42 weeks of gestation.
The aim of this prospective cross-sectional study was to establish new Doppler reference curves for peak blood flow velocities (Vmax, Vmean, Vmin) and impedance indices (PI, RI) of the middle cerebral artery at 18-42 weeks of gestation by an automatic wave form analysis integrated into the ultrasound device. In 962 low-risk pregnancies, blood flow velocities were derived from the middle cerebral artery with pulsed color Doppler ultrasonography. Reference curves were constructed for the individual parameters based on a growth function from a four-parameter class of monotonic continuous functions according to the smallest square principle for maximum blood flow velocities, as well as on a polynomial function for resistance indices. Further assessed was intra-observer reliability. The results obtained for maximum blood flow velocities demonstrate a continuous increase (Vmax = 26.8 cm/s to 59.1 cm/s, Vmean = 11.2 cm/s to 29.7 cm/s and Vmin = 4.9 to 15.8 cm/s) over the period from 18 to 42 weeks of gestation. In contrast, reference curves for the pulsatility and the resistance index are characterized by a parabolic pattern (18 weeks: 1.5; 28 weeks: 1.9; 42 weeks: 1.1 and 18 weeks: 0.68; 28 weeks 0.8; 42 weeks: 0.61). Intraobserver reliability for PI, RI, Vmax, Vmean, and Vmax were 87%, 83%, 80%, 83% and 93%, respectively. At constant measurement conditions, the reference ranges for blood flow velocities and impedance indices in the middle cerebral artery established by this study were found to be a useful non-invasive tool in risk assessment for fetal anemia, as well as in the Doppler ultrasound observation of the course in fetuses with intrauterine growth restriction.
Bahlmann
Franz
F
Department of Obstetrics and Gynecology, University of Mainz, Germany. bahlmann@mail.uni-mainz.de
Reinhard
Iris
I
Krummenauer
Frank
F
Neubert
Susanne
S
Macchiella
Doris
D
Wellek
Stefan
S
D000328:Adult; D001783:Blood Flow Velocity; D003430:Cross-Sectional Studies; D005260:Female; D005333:Fetus / Q000098:blood supply*; D005865:Gestational Age; D006801:Humans; D017078:Laser-Doppler Flowmetry; D020768:Middle Cerebral Artery / Q000502:physiology*; D015588:Observer Variation; D011247:Pregnancy; D011673:Pulsatile Flow; D012015:Reference Standards; D015203:Reproducibility of Results; D016216:Ultrasonography, Prenatal / Q000592:standards*