Uterine haemodynamics during pregnancy

Uterine blood flow (UBF) is measured using Doppler ultrasonography. Doppler indices from the uterine arteries (UA) provide a critical, quantitative assessment of placental vascular perfusion. Doppler ultrasound forms a significant part of the fetal health screen in women and is used increasingly to study utero–placental function in mares. Pulsed wave, colour Doppler ultrasonography identifies the direction of blood flow within a vessel and displays a spectral waveform of blood flow velocities. Doppler analyses include (1) waveform analysis, (2) calculation of resistance indices, and (3) direct measurement of blood velocities and flow. In human obstetrics, Doppler waveform analysis is the gold standard. For example, increased placental impedance may cause absent end diastolic flow in UA. Resistance indices are independent of the angle of insonation and are useful for curved or small blood vessels ...