To compare iron status at 24–28 weeks of pregnancy, 34 women diagnosed with GDM and 34 non-GDM women in the control group were tested for ferritin, hemoglobin (Hb), serum iron, mean corpuscular volume (MCV), total iron-binding capacity (TIBC) and mean corpuscular hemoglobin (MCH). This evidence concerns the gene GSTM1 and gestational diabetes.