Doppler indices from inferior vena cava and ductus venosus in predicting pH and oxygen tension in umbilical blood at cordocentesis in growth-retarded fetuses.

The objective of this study was to assess the value of Doppler indices calculated from the inferior vena cava and ductus venosus in the identification of acidemia and hypoxemia as determined by pH and gas analysis of fetal blood obtained by cordocentesis in growth-retarded fetuses. Doppler measurements were performed in the inferior vena cava and ductus venosus in 209 normally grown fetuses and in 89 growth-retarded fetuses. All growth-retarded fetuses were free from structural and chromosomal abnormalities, and uteroplacental insufficiency characterized by Doppler changes in the umbilical and middle cerebral arteries was the most likely etiology of the growth defect. In this group of fetuses, Doppler recordings were performed immediately before cordocentesis. Ten different indices were calculated from venous velocity waveforms, and reference limits for gestation were constructed by the cross-sectional analysis of data from normally grown fetuses. Logistic regression and receiver operator characteristic curve analysis were performed to examine the relationship between Doppler indices and acid-base status. The pre-load index (peak velocity during atrial contraction/peak velocity during systole) in the inferior vena cava was the best explanatory variable for acidemia (chi 2 = 48.33; p < or = 0.001). Hypoxemia was predicted less well by venous indices and the best results were achieved by the S/A ratio in the ductus venosus (chi 2 = 9.46; p < or = 0.005). In conclusion, our data suggest that acidosis in growth-retarded fetuses may be non-invasively identified by Doppler measurements of the inferior vena cava and that a higher efficiency can be achieved by the use of the pre-load index.