In addition, according to the PPH guidelines of the Society of Obstetricians and Gynecologists of Canada, the risk of PPH increases when the hemoglobin level is below 80 g/L, and the risk of PPH decreases by 0.86 for every 19 g/L increase in Hb (95% CI: 0.78–0.90) (26). This evidence concerns the gene GSTM1 and pulmonary arterial hypertension.