ASSESSMENT OF FETAL COMPROMISE BY DOPPLER ULTRASOUND INVESTIGATION OFTHE FETAL CIRCULATION - ARTERIAL, INTRACARDIAC, AND VENOUS-BLOOD FLOWVELOCITY STUDIES

Background Doppler studies of the fetal circulation in intrauterine gr owth retardation and hypoxia have demonstrated a compensatory redistri bution of arterial blood flow with increased flow to the cerebrum and myocardium and decreased flow to the periphery. The aim of this study was to evaluate the significance of changes in fetal venous blood flow waveforms in high-risk pregnancies and to investigate the time relati on between alterations in venous and arterial Doppler waveform indices in compromised fetuses. Methods and Results The cross-sectional study consisted of 108 high-risk singleton pregnancies between 23 and 42 we eks' gestation without fetal chromosomal abnormalities or major malfor mations. Blood flow velocity waveforms were recorded from the umbilica l arteries, descending thoracic aorta, middle cerebral artery, tricusp id and mitral ventricular inflow, ductus venosus, inferior vena cava, and the right hepatic vein. The mean velocity and pulsatility index we re calculated for arterial vessels, the E/A ratio for atrioventricular blood flow, and peak forward velocities during ventricular systole an d early diastole, the lowest forward velocity or peak reverse velocity during atrial contraction, and time-averaged maximum velocity for ven ous vessels. Two ratios for venous waveforms, one of which is the equi valent of the pulsatility index, were calculated Fetal biophysical ass essment was based on a computerized cardiotocogram and the biophysical profile score. The compromised group consisted of 37 fetuses delivere d by cesarean section for an abnormal heart rate trace (n=21) or sever e preeclampsia (n=9) or which died in utero (n=7) within 10 days of th eir last Doppler investigation. This group showed significant alterati ons in arterial and venous flow velocity waveforms but not in atrioven tricular inflow. Additionally, to find out whether venous Doppler inve stigation may help to detect a worsening of the situation in fetuses a lready showing arterial blood flow redistribution, we analyzed the dat a of these fetuses separately. The 41 fetuses that had an aorta/middle cerebral artery pulsatility index ratio >95th percentile were divided into compromised and noncompromised groups according to their biophys ical assessment and whether or not they developed fetal distress (cesa rean section for abnormal heart rate trace or intrauterine death). The mean values for Doppler parameters of the compromised groups differed significantly from the noncompromised groups in all venous vessels, w hereas differences on the arterial side were much less pronounced. Vel ocity ratios of venous waveforms were significantly higher, and absent or reverse flow in the ductus venosus with atrial contraction indicat ed a poor prognosis, with a perinatal mortality of 5 out of 8. Conclus ions Fetal compromise is associated with significant alterations in th e fetal arterial and venous circulation. Significant changes in venous Doppler waveforms develop due to increased afterload and perhaps myoc ardial failure in late deterioration after fetal arterial redistributi on is established and seem to be closely related to abnormal biophysic al assessment findings. Therefore, Doppler investigation of the fetal venous circulation may play an important role in monitoring the redist ributing growth retarded fetus and thereby may help to determine the o ptimal time for delivery.