Serial echo-Doppler measurements of human fetal abdominal aortic blood flow.

An echo-Doppler duplex scanner (DS) was used to make serial noninvasive measurements of human fetal abdominal aortic blood flow (Q). In 18 uncomplicated pregnancies (16 weeks to term), Doppler shifted frequency spectral waveforms (delta f), Doppler incident angles (theta), and peak systolic lumen diameters (D) were measured. Using the measured values of delta f and theta, the temporal average blood velocity (V) in the cardiac cycle was calculated from the Doppler equation. Values of Q were calculated using the equation: Q = pi X (D2/2) X V X HR, where HR is the heart rate. Gestational age (GA) and fetal weight (FW) were estimated from biparietal and transverse abdominal diameters. Each fetus was studied three to eight times at 2- to 4-week intervals. Results showed that Q increased nonlinearly with GA. Normalized to estimated FW, values of Q/kg did not vary significantly with estimated GA and gave an overall mean value (+/- standard deviation) during gestation of 184 +/- 35 ml/kg/min.