Results of subgroup analysis showed that Yimucao injection combined with oxytocin may be effectively reduces the intraoperative blood loss (SMD= -1.06, 95%CI= -1.34, -0.77, P<0.00001), blood loss within 2 hours (SMD= -1.33, 95%CI= -1.60, -1.06, P<0.00001), and blood loss within 24 hours after delivery (SMD= -1.46, 95%CI= -1.74, -1.19, P<0.00001) for preventing PPH compared with the oxytocin alone. This evidence concerns the gene OXT and pulmonary arterial hypertension.