degree of warning should be exerted with the everyday use of Doppler in pregnancy, due to the considerations related to heating/thermal effects from the high intensities of Doppler. Doppler assessment is demonstrated in scenarios where there is a risk of fetal growth restriction. diabetes mellitus chronic kidney disease hypertension prothrombotic states Pregnancy-related conditions suspected IUGR previous pregnancy with IUGR decreased fetal movement oligohydramnios polyhydramnios multifetal pregnancy Radiographic features Doppler ultrasound The spectral Doppler indices estimated at the fetal end, the free loop, and the placental end of the umbilical cord are dissimilar with the impedance. Waveform The umbilical arterial waveform has a "sawtooth" pattern with flow always in the forward direction, that is towards the placenta. An abnormal waveform shows absent or reversed diastolic flow. Before the 15th week, the absence of diastolic flow may be a normal finding The 95% confidence interval limit slowly decreases for both the resistive index (RI) Parameters The commonly used parameters are: The Doppler indices have been found to decline gradually with gestational age (i.e. there is more diastolic flow as the fetus matures): S/D ratio mean value decreases with fetal age at 20 weeks, the 50th percentile for the S/D ratio is 4 at 30 weeks, the 50th percentile is 2.83 at 40 weeks, the 50th percentile is 2.18 RI mean value decreases from 0.756 to 0.609 PI mean value decreases from 1.270 to 0.967