Fetal aortic blood flow and echocardiographic findings in human pregnancy

Relationships between human fetal aortic blood flow parameters and the corresponding echocardiographic findings were investigated in 51 normal, 26 hypertensive and 18 diabetic late pregnancies. In the normal pregnancies the time-averaged mean and peak velocities and the waveform indexes of the flow in the fetal aorta were not dependent on the cardiac size nor on the fractional shortening of the myocardium. Total blood flow in the aorta correlated well with heart size and left ventricular output. Hypertensive cases had, as a group, lower aortic velocities and higher waveform indexes than normal and diabetic pregnancies, and the difference from normal was particularly great if the fetus was growth-retarded. Myocardial contractility in these fetuses remained good in spite of these peripheric hemodynamic alterations, but the relative size of the right ventricle was increased. The diabetic cases had smaller blood flow volume in fetal aorta than in the normal cases. In contrast with normal pregnancies the myocardial fractional shortening of these fetuses decreased if the pulsatility of the aortic blood flow increased or the total blood flow in the aorta was high. These findings point to a decreased functional capacity of the fetal heart in a diabetic pregnancy, in particular in the late weeks of gestation.