Bottom Line: We are terrible at estimating how much blood people are losing just by looking at it. Use calibrated drapes (drapes with markings that tell you how much blood is being lost), or just a large bag and then weigh it afterwards (1g ~ 1ml of blood loss).
In 2025, Yunas et. al did a systematic review to look at how we evaluate blood loss in the postpartum period, defining postpartum hemorrhage (PPH) as >500ml and severe postpartum hemorrhage as >1000ml.
What they found was that visual estimation or relying on the provider's eyes was only 50% sensitive in identifying PPH and only 10% sensitive in identifying severe PPH, which means that we miss up to 90% of severe PPH when we just look at the blood.
Well, what do we do about that?
Per FIGO recommendations and the Yunas et. al study, gravimetric methods (or measuring everything that was soaked in blood and subtracting out the dry weight) are the most accurate, but they're very time-intensive, so an easier method is volumetric (having the patient bleed into a bag or bucket that has lines telling you how much volume of blood has been lost), especially calibrated drapes (pictured below). These are drapes designed for this purpose that can be placed under the patient. These are fairly cheap and should be in every ED as preparation for a precipitous delivery and potential PPH.
If your hospital doesn't have them and is unwilling to get them, you could use other large bags, such as trash bags, large patient belonging bags and weight these afterwards, subtracting the dry weight of the bag (1g ~ 1ml of blood).
Regardless of what you choose to do - DO NOT RELY ON YOUR EYES. THEY ARE NOT DEPENDABLE.
Begum F, Nieto-Calvache AJ, Schlembach D, et al. FIGO recommendations on objective measurement of blood loss after birth for early detection of postpartum hemorrhage. Int J Gynaecol Obstet. 2025;171(3):933-950. doi:10.1002/ijgo.70523
Yunas I, Gallos ID, Devall AJ, Podesek M, Allotey J, Takwoingi Y, Coomarasamy A. Tests for diagnosis of postpartum haemorrhage at vaginal birth. Cochrane Database Syst Rev. 2025 Jan 17;1(1):CD016134. doi: 10.1002/14651858.CD016134. PMID: 39821088; PMCID: PMC11740288.
