We have already shown in our study population that adapting prenatal iron supplementation (80, 40, and 20 mg) to early pregnancy iron levels (normal, Hb 110–130 g/L, or normal-high Hb > 130 g/L) in non-anaemic women, prevents iron imbalances during pregnancy, both due to iron deficiency and excess [39]. This evidence concerns the gene GSTM1 and nutritional disorder.