Figure 2B–E show the perioperative trends of maternal hemoglobin (Hb) and hematocrit (Hct) (Figure 1, Analysis 1). Fe supplementation is a standard and effective strategy for treating anemia; however, the combination of oral Fe plus Zn supplementation resulted in slightly significant negative effects on postoperative day 6 compared to oral Fe supplementation only (Figure 2B,C). This evidence concerns the gene GSTM1 and anemia (phenotype).