Obstetric hemorrhage risk assessment using the maximum allowable blood loss calculation: are we on the right track?

The clinical guidelines on postpartum hemorrhage from the Society of Obstetricians and Gynaecologists of Canada (SOGC) provide evidence-based recommendations structured around the 6Rs framework: Risk Assessment, Risk Reduction, Recognition and Evaluation, Reaction, Resuscitation, and Review. Since its publication, our institution has begun implementing all the guideline recommendations. One key recommendation is to calculate the Maximum Allowable Blood Loss (MABL) to reach a hemoglobin level of 70 g/L for every obstetric patient. This practice was introduced to promote an individualized approach to hemorrhage risk assessment, accounting for variations in patients' anthropometric characteristics. However, there is currently a lack of evidence supporting the use of MABL calculation in the obstetric population. In this commentary, we highlight the limitations of the MABL calculation through specific examples and propose areas for further research.