Ductus venosus Doppler study in fetuses with homozygous α-thalassemia-1 at 12 to 13 weeks of gestation

Objective Fetuses affected by homozygous alpha -thalassemia-1 are anemic from the first trimester of pregnancy. We investigated ductus venosus Doppler velocimetry in these affected fetuses at 12-13 weeks of gestation. Design Prospective observational study. Subjects Women referred for the prenatal diagnosis of homozygous alpha -thalassemia-1 before 14 weeks of gestation. Methods All fetuses underwent pulsed Doppler investigations following color flow mapping at 12 or 13 weeks of gestation. Homozygous alpha -thalassemia-1 was diagnosed by DNA or hemoglobin study. The ductus venosus Doppler indices - V-max (peak velocity during ventricular systole), V-min (minimum forward velocity during atrial systole), TAMX (time-averaged maximum velocity), PIV (pulsatility index for veins, V-max - V-min/TAMX), PLI (preload index, V-max - V-min/V-max) and V-max/V-min ratio - were compared between the affected fetuses and fetuses unaffected by homozygous alpha -thalassemia-1. Results Between June 1998 and October 1999, 102 eligible women were recruited. Fetal ductus venosus Doppler study was successful in 96 pregnancies (94%). Of these, 20 fetuses were affected by homozygous alpha -thalassemia-1. None of them showed hydropic changes as the time of Doppler study. The affected fetuses had significantly higher ductus venosus V-max (30% increase), V-min (50% increase) and TAMX (20% increase) and significantly lower V-max/V-min ratio, PIV and PLI values. Conclusion Fetuses affected by homozygous alpha -thalassemia-1 at 12-13 weeks had increased forward flow velocities in the ductus venosus throughout the cardiac cycle. The increase of venous return is consistent with our previous report of cardiac dilatation and an increase of cardiac output in the affected fetuses at this stage as a compensatory mechanism for anemia and hypoxia. However, extensive overlap of the ductus venosus Doppler indices between affected and unaffected fetuses precludes its use in predicting anemia at 12-13 weeks.