GSTM1 and anemia (phenotype): A physiological decrease in Hb concentration occurs due to hemodilution and an assumed decrease in erythrocyte life span, partially offset by an increase in erythropoietin (EPO) concentrations and erythrocyte mass.35, 38, 39, 40 Furthermore, iron deficiency is an important contributing factor to the anemia of pregnancy, because iron utilization for maternal red blood cell expansion and fetoplacental growth exceeds the supply of iron from diet (Table 1).32