Time-domain ultrasonography is an alternative to Doppler analysis of blood flow direction and velocity. The technique uses timing information between successive echo pulses to measure flow velocities directly through a color display map. Volume flow quantification also can be achieved by combining time-domain methods with M-mode ultrasonography. This report describes our preliminary experiences with fetal vascular imaging by time-domain ultrasonography, compares Doppler peak velocity correlation to time-domain sonography, and examines the in vitro accuracy of time-domain sonography combined with M-mode volume flow measurements. Excellent agreement was found between peak Doppler velocity measurements and time-domain ultrasonography for a variety of maternal and fetal vessels (N = 29). Close volume-flow correlation was observed between a flow pump and time-domain ultrasonography under constant and pulsatile conditions. Time-domain ultrasonography appears to be a useful alternative to Doppler techniques for imaging small fetal vessels and also may provide the basis for accurate volume flow measurements during pregnancy.