o_1977r8vv9vk1ts2ms0kd8pksa.pdf

214 J. C. Veille
Fig. 15.5 a±c. Normal Doppler changes. a Longitudinal
study of the fetal renal peak flow velocity
(PFV) in normally grown fetuses across gestation.
There is a slight but nonsignificant increase in
PFVwith advancing age. b Longitudinal study of
the systolic-to-diastolic (S/D) ratio in normal
fetuses across gestation. There is no significant
change in the S/D ratio of the fetal renal artery
as gestation advances. c Longitudinal study of
the time velocity integral (TVI) (area under the
curve) in normal fetuses across gestation. TVI
progressively increases with advancing gestation
of gestation. In the normal human fetus, impedance
to flow in the renal artery decreased with advancing
gestational age [11]. In more than 54% of these normal
fetuses the renal artery had an absent end-diastolic
Doppler velocity. A high-pass filter of 125 Hz
was used which may have obstructed low levels of
end-diastolic flow. Hecher et al. reported on duplex
Doppler ultrasonography in one normal human fetus
studied at week 22 of gestation, seven fetuses studied
between weeks 32 and 35, and 12 fetuses studied between
weeks 36 and 40 [12]. They noted that end-diastolic
flow was absent in four of the seven fetuses
studied between weeks 32 and 35 (or 4 of 20 fetuses,
> 20%) despite normal growth and normal amniotic