This observation indicates that, in the first case, an iron dose higher than that usually prescribed in Spain (40 mg/day) compensated for the low iron stores that could have undermined the children's behavioural development at 4 years of age, although the Hb levels did not indicate the presence of anaemia, which until now would not have justified the prescription of higher prenatal doses of iron in routine clinical practice. Here, GSTM1 is linked to anemia (phenotype).