If serum ferritin is low (<30 μg/L), but the Hb is normal (≥11 g/dL during the 1st trimester, ≥10.5 g/dL during the 2nd trimester, and ≥11 g/dL during the 3rd trimester) the diagnosis is iron deficiency; however, if serum ferritin is low (<30 μg/L) and Hb is also low (<11 g/dL during the 1st trimester, <10.5 g/dL during the 2nd trimester, and <11 g/dL during the 3rd trimester), the diagnosis is iron deficiency anemia. This evidence concerns the gene GSTM1 and Iron deficiency anemia.