Does in-utero transfusion for homozygous α0-thalassemia depend on hemoglobin level alone?

Abstract

Objectives: To determine hematological parameters in fetusesaffected by α0-thalassemiaMethods: This was a retrospective cross-sectional study of 546 fetalor cord blood collected at 12–40 weeks’ gestation for the prenataldiagnosis of α0-thalassemia or other indications from 1993 to 2006.The proportion of hemoglobin (Hb) fractions was determined byelectrophoresis of hemolysate on cellulose acetate.Results: In homozygous α0-thalassemia (n = 183), the median Hblevel, proportion of Hb Bart’s(γ4) and Hb Portland 1(ξ2γ2)were6.4 g/dl, 77.5% and 22.5% respectively. While the Hb level andthe proportion of Hb Bart’s increased significantly with gestation,the proportion of Hb Portland 1 (ξ2γ2) decreased. Although mildanemia (with reference to the gestation) was present in 27.5% of the affected fetuses, the mean Hb level contributed by HbPortland 1(ξ2γ2), with normal ability to release oxygen, was only1.4 g/dl from 12 to 40 weeks’ gestation. There were no differences inthe hematological parameters between hydropic and non-hydropicfetuses. In one affected case, the middle cerebral artery peaksystolic velocity (MCAPSV) was 49cm/s (> 1.5MoM) at gestation of21 weeks. Cordocentesis showed Hb level of 6.5 g/dl, hematocrit of0.266, pO2 of 6.2 kPa, and pH of 7.42. First in-utero transfusion(IUT) was given. At 29 weeks’ gestation, MCAPSV was increasedagain to 56 cm/s (> 1.5MoM). Cordocentesis showed mild anemia(Hb of 9.1g/dl), but acidosis (pH of 7.35) and hypoxia (pO2 of3.4kPa). After correction of fetal anemia by the second IUT, boththe fetal pH (7.43) and pO2 (6.9 kPa) returned to normal. Theaffected baby was subsequently delivered at term, and survived.Conclusion: Although the degree of anemia is mild in around one-quarter of the affected fetuses, the Hb level contributed by HbPortland 1(ξ2γ2) is very low in all affected fetuses from 12 weeks’gestation. Whether to give IUT to an affected fetus depends not juston fetal Hb level, but also on ultrasound signs of severe anemia,oxygen and pH status.