see Thalassemias

The homozygous α°-thalassemia  does not contain any α chain and causes hydrops fetalis (hydrops fetalis with death in utero or neonatal) and a clinical picture of pre-eclampsia or eclampsia in the mother. Hemoglobin Bart is formed by the tetramerisation of surplus γ chains:  there is 10-40 % of hemoglobin Bart in the blood of newborn affected by α thalassemia.