FETAL CENTRAL BLOOD-FLOW ALTERATIONS IN HUMAN FETUSES WITH UMBILICAL ARTERY REVERSE DIASTOLIC FLOW

Blood flow velocimetry studies in animal fetuses with reverse diastoli c flow in the umbilical artery have shown marked changes in the fetal central circulation characterized by a retrograde diastolic flow in th e descending aorta, and as far as the aortic arch, along with a signif icant forward diastolic flow in the arteries going to the brain. Docum entation and the implications of this phenomenon in human fetuses, to date, have not been reported. Doppler echographic evaluations of the d iastolic patterns in the umbilical artery, descending aorta, the aorti c arch, and the common carotid artery were performed on 5 fetuses in w hom reverse diastolic flow was observed in the umbilical artery. In al l five cases reverse diastolic flow was observed not only in the umbil ical artery but also in the aortic arch. In the carotid artery, howeve r, a forward diastolic flow was always recorded. It can be concluded, by inference, that in these fetuses, the area of lowest resistance was no longer the placenta, as seen in normal conditions, but the cerebra l circulation. Furthermore, in four fetuses the retrograde component o f the flow profiles was more prominent in the aortic arch compared wit h the descending aorta, suggesting that, in diastole, blood was coming from the pulmonary artery through the ductus arteriosus.