GSTM1 and hydrops fetalis: These include thalassemia major (co-inheritance of two mutations of the beta chain); sickle cell syndromes (Hb S, Hb SS, Hb SC, Hb S/thalassemia, Hb SD, Hb SOArab, Hb Lepore and Hb SE); Hb E/thalassemia (co-inheritance of mutations for thalassemia with Hb E); Hb H disease; and Hb Bart's hydrops fetalis [homozygous for alpha thalassemia (α-thal) genotype --/--].1, 3