In one study, almost 20% of women with severe PPH, defined by fulfillment of at least one of the following criteria: transfusion of red blood cell concentrates, conservative surgery for PPH, arterial embolization, hysterectomy, transfer to intensive care unit due to PPH, death attributed to PPH, or hemoglobin (Hb) decrease by > 4 g/dl, were diagnosed solely on the basis of laboratory tests7. This evidence concerns the gene GSTM1 and pulmonary arterial hypertension.