Haemoglobin level, proportion of haemoglobin Bart's and haemoglobin Portland in fetuses affected by homozygous α0-thalassemia from 12 to 40 weeks' gestation

Objectives To determine haematological parameters in fetuses affected by homozygous α0-thalassemia. Methods This was a cross-sectional retrospective study reviewing 546 blood samples (268 fetal and 278 neonatal cord) being collected between 1993 and 2006, from 12 weeks' gestation onwards for any indication, including the prenatal diagnosis of homozygous α0-thalassemia, other haematological disorders, hydrops or aneuploidy. The proportion of haemoglobin (Hb) fractions was determined by electrophoresis of haemolysate on cellulose acetate in all samples. Results There were significant differences in the haematological parameters between homozygous α0-thalassemia (n = 183) and control (n = 363) which were either heterozygous α0-thalassemia (alpha thalassemia trait) or normal. In homozygous α0-thalassemia, the median Hb level, proportion of Hb Bart's (γ4) and Hb Portland 1(ζ2γ2) were 6.4 g/dL, 77.5% and 22.5%, respectively. While the Hb level and the proportion of Hb Bart's increased significantly with gestation, the proportion of Hb Portland 1 decreased. The Hb level contributed by Hb Portland 1 remained around 1.4 g/dL throughout gestation. The proportion of mild, moderate and severe anaemia in the affected fetuses was 27.5, 32.7 and 39.8%, respectively. There was no significant difference in these proportions across different gestation (P = 0.231). There were no differences in the haematological parameters between hydropic and non-hydropic fetuses. Conclusion Although the degree of anaemia is mild in around one-quarter of the affected fetuses, the contribution by Hb Portland 1 (ζ2γ2) to the Hb level was very low throughout gestation, and the affected fetuses may therefore be at risk for hypoxia. Copyright © 2010 John Wiley & Sons, Ltd.