Rethinking Postpartum Hemorrhage Thresholds: A Global Meta-Analysis on Prognostic Markers
- FHS Communications
Although effective treatments exist, postpartum haemorrhage (bleeding after giving birth) remains a leading cause of maternal mortality. The main reason for this is that women at risk of this complication are not identified early enough to ensure adequate intervention that could be lifesaving. Because of the lack of large-scale studies from diverse populations, there is no consensus on how to identify women at risk of postpartum haemorrhage.
To address this need, a global study published in The Lancet in October 2025, titled ‘Prognostic accuracy of clinical markers of postpartum bleeding in predicting maternal mortality or severe morbidity: a WHO individual participant data meta-analysis' led by the World Health Organization (WHO) analysed individual participant data from over 300,000 women across 23 countries to assess the prognostic accuracy of various clinical markers in predicting maternal death or severe morbidity following childbirth. The study showed that traditional clinical thresholds for postpartum haemorrhage may not be sensitive enough for predicting life-threatening maternal outcomes.
In the study, the thresholds of five key clinical indicators, including measured blood loss, pulse rate, systolic and diastolic blood pressure, and the shock index (pulse divided by systolic blood pressure), were used to assess the sensitivity of these markers in predicting adverse maternal death or severe morbidity. Traditionally, postpartum haemorrhage has been diagnosed when a woman loses 500 mL or more of blood after giving birth. However, this study suggests that waiting for blood loss to reach this threshold may be too late to protect mothers at risk.
Sensitivity of balance
To determine a new acceptable blood loss threshold, researchers lowered the threshold to 300 mL, which improved the identification of women who will progress to experience maternal death or severe morbidity due to postpartum haemorrhage. However, this reduced the risk factor for women who will not experience severe outcomes from 81% at the historical threshold to 54%. This trade-off highlights the importance of balancing early detection with diagnostic precision. When assessing vital signs alone, they were less reliable as markers, as only one met the WHO’s optimal criteria of over 80% sensitivity and at least 50% specificity when used in isolation. The researchers suggest that the lower blood-loss threshold, combined with early warning signs such as an abnormal pulse, blood pressure, or shock index, is far better at identifying women in danger of severe illness or death. These vital signs are already part of widely used maternal early-warning systems, so incorporating the new criteria could be relatively easy in many facilities.
Social impact
The combined approach improves early detection, especially after vaginal births, allowing clinicians to identify and treat postpartum haemorrhage earlier. This will potentially reduce maternal mortality, especially in low-resource settings where delays in care can be fatal. However, it is likely to increase the number of diagnoses of postpartum haemorrhage, particularly in hospitals that are newly adopting more accurate methods for measuring blood loss or managing caesarean births. This shift will have resource implications, including training demands and changes to clinical workflow, but the potential benefits for maternal survival are significant.