Summary estimates were created for the relationship of high Hb to post-partum hemorrhage, transfusion, pre-eclampsia, gestational diabetes, postpartum depression, prenatal depression, and maternal mortality by Hb concentration cutoff: ≥130, ≥ 140, and ≥ 150 g/L (Table 4). This evidence concerns the gene GSTM1 and postpartum depression.