Methods used by health care professionals to quantify blood loss during vaginal birth: a scoping review

Blood loss during vaginal birth is commonly assessed using estimated blood loss and quantified blood loss; however, estimated blood loss is frequently criticized for inaccuracy.

Postpartum hemorrhage is a major cause of preventable maternal morbidity and mortality worldwide. Although many cases are preventable through early recognition and timely management, inaccurate assessment of blood loss remains a concern.

We aimed to identify and map methods for measuring blood loss during vaginal birth.

A scoping review was conducted using the Arksey and O'Malley framework and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews. Four databases (PubMed, CINAHL, Cochrane CENTRAL, Ichushi-Web) were searched from inception to April 2025. Studies describing methods for quantifying blood loss during vaginal birth were included regardless of design. Extracted data included measurement method, tools, assessors, timing, and indicators of reliability or accuracy.

Twenty-four studies met our inclusion criteria. Blood loss was measured using heterogeneous approaches-visual estimation, calibrated drapes and collection bags, gravimetric techniques, hemoglobin/hematocrit-based calculations, and mixed methods. Visual estimation was the most common approach, but it consistently underestimated blood loss, particularly >500 mL. Objective methods showed moderate to high correlation with hemoglobin/hematocrit changes.

Although objective measurements demonstrated greater accuracy, they required dedicated equipment, standardized procedures, and trained personnel. Facility resources and staff skills strongly influenced accuracy and feasibility of blood loss measurement methods. Measurement of blood loss during vaginal birth is highly variable, and commonly used visual estimation demonstrates limited accuracy.