ObjectiveTo determine if quantification of blood loss (QBL) would result in fewer activations of postpartum hemorrhage (PPH) protocols than visual estimation of blood loss (EBL) after cesarean birth and to track the use of related resources. DesignProspective observational trial. SettingA tertiary academic medical center in the midwestern United States. ParticipantsA total of 42 cases of cesarean birth. MethodsWe visually estimated blood loss during cesarean birth and quantified blood loss with colorimetric testing after the surgery. We compared EBL to QBL in four categories, from no hemorrhage to severe PPH, and documented resources used for women placed on the institutional PPH protocol by EBL who did not meet criteria for PPH by QBL. ResultsThe median EBL was 1,275 ml (interquartile range = 1,100–1,510 ml), and the median QBL was 948 ml (interquartile range = 700–1,267 ml, p < .001). Twenty-four (57%) instances of PPH based on visual EBL would not have been classified as such based on QBL. The most frequently used resources in these cases included laboratory testing and administration of uterotonics. ConclusionUse of QBL during cesarean births would have reduced the number of identified PPHs by more than 50% over visual EBL and may have reduced the resources used as part of care.