Comparison of the prognostic value of pulsed Doppler blood flow parameters to predict SGA and fetal distress.

A total of 219 women with complicated pregnancies had Doppler assessment of uteroplacental arteries, the umbilical artery, the fetal common carotid artery and the descending thoracic aorta to determine the prognostic value of Doppler examinations to predict the birth of a small-for-gestational-age (SGA) infant with or without fetal distress. Preliminary reproducibility studies showed that the resistance index, pulsatility index and intensity weighted flow velocity had the lowest coefficients of variation. Data on the systolic/diastolic ratio and mean blood flow volume were, therefore, not considered for further evaluation. Measurements were classified according to the time interval of the examination to the delivery of the baby according to the following groupings: 0-14 days, 15-28 days and 29-42 days. For evaluation of the SGA fetus complicated by fetal distress, only measurements within 2 weeks of delivery were analyzed. Significant differences were calculated by considering the area below the receiver operator characteristic (ROC) curves. Only Doppler studies of the uteroplacental arteries (mainly resistance index) were predictive of the later development of the SGA fetus. All fetal parameters showed an increasing improvement in the predictive capacity for an SGA infant, the closer the measurements were made to the time of delivery. This improvement was not observed for uteroplacental vessels. The resistance index of the uteroplacental vessels was significantly higher in SGA pregnancies complicated by fetal distress compared to SGA pregnancies alone. However, ROC analysis revealed that fetal Doppler velocimetry was more strongly related to fetal distress than SGA only. The single best fetal parameter was the mean velocity in the fetal descending thoracic aorta but the velocity ratio of the fetal common carotid artery over the fetal descending thoracic aorta had the highest predictive capacity for the SGA pregnancy complicated by fetal distress.