A total of 3,880 (78.6%) fetuses were at risk for severe thalassemia diseases, including Hb Bart’s hydrops fetalis caused by homozygous α0-thalassemia, Hb E-β0-thalassemia, homozygous β0-thalassemia, compound heterozygous for β0/β+-thalassemia and compound δβ0/β0-thalassemia. Here, GSTM1 is linked to hydrops fetalis.