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A real time sector scanner with a pulsed Doppler transducer was used to study and compare the blood flow velocity wavefroms of fetal descending thoracic aorta in 97 normal pregnancies and 50 cases of fetal growth retardation with 170 and 67 examinations, respectively. All pregnancies were in the third trimester. In both groups, A / B ratio, resistance index, and pulsatility index remained unchanged with increasing gestational age. In growth reatarded pregnancies, there were singnificant increases in A / B ratio, pulsatility index, and resistance index, and significant decrease in end diastolic velocity compared to those in normal pregnancies(p<0.05), reflecting increased peripheral vascular resistance. In the 8 distressed fetuses, Doppler findings were more pathological than those in the fetuses without distress. This method may be of value in the evaluation of fetal well-being in risk pregnancies by giving an early sign of hemody namic changes in developing hypoxia.
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