In the primary analysis of this study14, we demonstrated that approximately 50% of women with Hb < 10.5 g/dL at delivery developed moderate to severe postpartum anemia (Hb ≤ 9.5 g/dL), for which intravenous iron sucrose treatment is advised by our departmental protocol and by others14,23,24. The gene discussed is GSTM1; the disease is anemia (phenotype).