Lower blood loss thresholds combined with abnormal vital signs could identify women at risk of life-threatening postpartum haemorrhage earlier than current definitions, according to a large global meta-analysis.
Global Analysis Of Bleeding Markers
Postpartum haemorrhage is a leading cause of maternal mortality and morbidity worldwide, yet there is no global consensus on which clinical markers best define excessive bleeding or predict adverse outcomes. To address this, researchers conducted an individual participant data meta-analysis to assess the prognostic accuracy of commonly used clinical markers.
Eligible datasets were identified through a World Health Organization global call for data and systematic searches of major databases up to November 2024. Studies were required to include at least 200 women with objectively measured blood loss or haemodynamic markers and to report relevant maternal outcomes. Of 33 potentially eligible datasets, 12 provided full data, comprising 312,151 women.
Five markers were assessed: measured blood loss, pulse rate, systolic blood pressure, diastolic blood pressure and shock index. The primary outcome was a composite of maternal death or severe morbidity, including blood transfusion, surgical intervention or admission to intensive care.
Blood Loss Alone Misses Risk
At the conventional threshold of 500 mL, measured blood loss had a prognostic sensitivity of 75.7% and a specificity of 81.4% for predicting the composite outcome. Although specificity was high, sensitivity did not reach the level preferred for early identification of women at risk.
Lowering the threshold improved sensitivity. At 300 mL, sensitivity increased to 83.9%, but specificity fell to 54.8%, highlighting the limitations of relying on blood loss volume alone to guide clinical decisions.
Vital Signs Add Predictive Power
Prognostic performance improved when blood loss was combined with haemodynamic signs. Decision rules that used blood loss below 500 mL together with any abnormal vital sign, including pulse rate above 100 beats per minute, systolic blood pressure below 100 mm Hg, diastolic blood pressure below 60 mm Hg or shock index above 1.0, achieved sensitivities between 86.9% and 87.9%. Specificities ranged from 66.6% to 76.1%.
Women with blood loss of 500 mL or more were also consistently identified as high risk. The combined approach more accurately identified women likely to experience death or severe complications, even when bleeding volumes were below traditional thresholds.
The authors conclude that recognising postpartum haemorrhage at lower blood loss volumes, alongside abnormal haemodynamic signs, could support earlier diagnosis and treatment, with potential to reduce preventable maternal deaths worldwide.
Reference
Gallos I et al. Prognostic accuracy of clinical markers of postpartum bleeding in predicting maternal mortality or severe morbidity: a WHO individual participant data meta-analysis. The Lancet. 2025;406:10514;1969-82.
