PURPOSE: to determine the relationship between the Doppler indices of inferior vena cava and ductus venosus and the fetal hemoglobin concentration. METHODS: a cross-sectional prospective study was performed at the "Centro de Medicina Fetal HC UFMG" from January 1998 to July 2001. Thirty-one pregnant women with isoimmunization, detected by an indirect Coombs test >1:8, underwent a protocol for the identification of fetal hemolysis. When intrauterine transfusions were indicated, the umbilical cord hemoglobin concentration was measured at the begining of the procedure. In the other cases, it was measured at delivery. Every single intrauterine transfusion preceded by Doppler flow velocity waveforms from inferior vena cava and ductus venosus was defined as one case. Hemocue® (B-Hemoglobin Photometer Hemocue AB; Angelholm, Sweden) was used to measure the fetal hemoglobin concentration. In all cases, inferior vena cava and ductus venosus Doppler examinations were performed before the collection of fetal blood samples. For the inferior vena cava Doppler, the studied indices were pulsatility index for veins (PVI), peak velocity index for veins (PVIV) and atrial/systole ratio (CA/SV ratio or preload index); for ductus venosus, PVI, PVIV and systole/atrial ratio (SV/CA ratio). The relationship between inferior vena cava and ductus venosus Doppler indices and cord blood hemoglobin concentration was obtained by simple linear regression analysis. Moreover, an association between those indices and the finding of fetal hemoglobin <10 g/dL was shown by the c² test, significant at p<0.05. RESULTS: seventy-four procedures were studied. In twenty-three cases fetal hemoglobin was below 7 g/dL. A significant negative correlation between all studied Doppler indices and fetal concentration of hemoglobin was observed (p<0.05). The highest Doppler index values were observed in severe anemic fetuses. Fetuses with cord blood hemoglobin below 10 g/dL presented inferior vena cava and ductus venosus Doppler indices over the 95 percentile for gestational age. CONCLUSIONS: Doppler flow velocity waveforms from inferior vena cava and ductus venosus may be used as a noninvasive marker of severe fetal anemia.
Venous Doppler; Ductus venosus; Inferior vena cava; Rhesus isoimmunization
