[Association between postpartum blood loss volume and maternal adverse clinical outcomes]

Objective: To investigate the relationship between postpartum hemorrhage (PPH) volume and the risk of adverse clinical outcomes in pregnant women. Methods: This was a retrospective cohort study of 41 494 deliveries at Peking University Third Hospital from 2012 to 2020. With PPH volume as the main exposure, the outcome indicators included: (1) Severe adverse outcomes: shock or embolism, abnormal coagulation function, abnormal liver function, and kidney injury; (2) General adverse outcomes: moderate to severe anemia, hypoalbuminemia, postpartum blood transfusion. Robust Poisson regression was employed to calculate the risk of each outcome index in pregnant women with different PPH volumes under the condition of controlling confounding factors, and to analyze the risk trends of each outcome index with the change of PPH volumes. Results: A total of 41 494 pregnant women were included in the study, including 9 959 cases (24.00%, 9 959/41 494), 23 974 cases (57.78%, 23 974/41 494), 5 235 cases (12.62%, 5 235/41 494), 1 144 cases (2.76%, 1 144/41 494), 508 cases (1.22%, 508/41 494), 208 cases (0.50%, 208/41 494), 207 cases (0.50%, 207/41 494) and 259 cases (0.62%, 259/41 494) pregnant women with PPH volume <250, 250-499, 500-749, 750-999, 1 000-1 249, 1 250-1 499, 1 500-1 999 and ≥2 000 ml, respectively. The risk of any serious adverse outcome, such as shock or embolism, abnormal coagulation function, abnormal liver function and kidney injury, showed a "J-shaped" relationship with PPH volume: risks remained stable (0.26%-0.59%) below 1 500 ml but increased significantly to 3.38% (RR=3.43, 95%CI: 1.14-10.35) at 1 500-1 999 ml and 5.02% (RR=4.53, 95%CI: 1.49-13.75) at ≥2 000 ml (all P<0.05). Moderate-to-severe anemia showed threshold effects at 750 ml (RR ranging from 7.21 to 8.53) and hypoalbuminemia at 1 250 ml (RR ranging from 3.24 to 3.83), with risks plateauing beyond these thresholds (all P<0.05). Conclusion: It is suggested that 750 ml, 1 250 ml and 1 500 ml should be used as the key intervention thresholds, corresponding to the initiation thresholds of anemia, hypoalbuminemia management and multidisciplinary intensive care, respectively, so as to provide a new reference for optimizing the clinical diagnosis and treatment strategy of PPH.