In a subanalysis of women categorized according to Hb level between weeks 24–30 (≤ 10.6 g/dL) and iron supplementation use (frequent versus infrequent; Table 3), women with Hb < 10.6 g/dL showed a two-fold higher risk for anemia at delivery when using iron supplements infrequently as compared to those reporting frequent use of iron supplements (44% versus 25%, p = 0.03). This evidence concerns the gene GSTM1 and anemia.