In the case of a lack of response to oral iron (Hb levels rising by less than 10 g/L within 14 days), severe iron-deficiency anemia, intolerance of oral iron, or clinical need for rapid and efficient treatment of anemia (e.g., advanced pregnancy), intravenous iron therapy should be administered in the absence of contraindications but not before 16 weeks of gestation [44]. The gene discussed is GSTM1; the disease is anemia (phenotype).