report greater odds of both low birth weight and preterm birth associated with iron deficiency anemia (IDA) compared with non‐IDA.26 It is estimated that approximately 50% of anemia among nonpregnant and pregnant women is responsive to iron supplementation;27 however, at the national and subnational level, the percentage of anemia that is IDA has been shown to be extremely variable, ranging from <1% to 75%.28 Whether the etiology of anemia affects relationships between Hb concentrations and health outcomes merits closer examination. The gene discussed is GSTM1; the disease is anemia (phenotype).