Volume blood flow estimation in the normal and growth-restricted fetus

The objective was to compare volume blood flow (VBF) in the descending aorta (DAo) of gestational age and weight-matched growth restricted (GR) and normal (N) fetuses. A longitudinal study of 20 N was compared with 11 GR in two analyses matched for weight and gestation. DAo dimensions and flow velocity were measured simultaneously using a new technique combining an ultrasonic phase-locked echo-tracking system synchronized with a pulsed Doppler velocimeter. Cardiac output was estimated using standard echocardiographic views. DAo and semilunar valve diameters increased linearly in N and indexed cardiac output was similar in N and GR, although GR showed reduced DAo relative pulse amplitude, mean flow velocity and VBF. This synchronized technique permits calculation of VBF in human fetuses. Growth restriction is associated with reduced aortic wall pulsations and lower mean blood flow velocities and VBF in DAo secondary to increased placental impedance.