The amounts of Hb Bart’s corresponded with the severity of α-globin gene defects, i.e., highest in the Hb Bart’s hydrops fetalis (81.5 ± 3.6%) followed by Hb H disease, homozygous Hb CS, double α+-thalassemia/Hb CS, α0-thalassemia trait, and α+-thalassemia trait, as shown in Fig. 5. This evidence concerns the gene GSTM1 and hydrops fetalis.