Fig. 1From: Reference ranges of fetal superior vena cava blood flow velocities and pulsatility index in the second half of pregnancy: a longitudinal studyDoppler recording of the fetal superior vena cava blood velocity waveforms showing systolic peak velocity (S), diastolic peak velocity (D), and velocity deflection during atrial contraction (A). Interference by the systolic peak in the ascending aorta (AAo) seen below the zero lineBack to article page