A total of 645 (13.1%) fetuses were classified in this study as a group of unnecessary PND as they were at risk of having other mild forms of thalassemia, including α-thalassemia diseases (Hb H disease, Hb H-Constant Spring disease, and homozygous Hb Constant Spring) (n = 58, 1.2%), β+-thalassemia (n = 168, 3.4%), high Hb F determinants (n = 109, 2.2%), and abnormal Hbs (n = 16, 0.3%). This evidence concerns the gene GSTM1 and thalassemia.