GSTM1 and gestational diabetes: Although the mechanisms by which Hb, RBC, MCHC influence GDM or vice versa are not well understood, researchers suggested some mechanisms for such association; it has been reported that insulin resistance, the hallmark of GDM, may disrupt iron metabolism and erythropoiesis at multiple steps, leading to a suboptimal haemoglobin concentration within the RBCs [48, 49].