In addition, many couples at risk carried more than one thalassemia genotypes and therefore had the risk of having fetuses with more than one severe thalassemia diseases, e.g., both Hb Bart’s hydrops fetalis & Hb E-β0-thalassemia and homozygous β0-thalassemia & Hb E-β0-thalassemia. This evidence concerns the gene GSTM1 and hydrops fetalis.