Prospective Validation of Formulae for the Estimation of Intrapartum Blood Loss [21N]

INTRODUCTION: Postpartum hemorrhage (PPH) is a leading cause of maternal morbidity and mortality. Improving the accuracy of blood loss estimation is vital to the clinical management of postpartum women. In this study we prospectively validated formulae previously derived to estimate blood loss, that were identified through a systematic review. METHODS: Pregnant women over 18 years of age delivering after 24 weeks gestational age were included. Participants had blood loss measured by reference standards that included gravimetric and direct measurement methods and by calculated estimation involving the use of formulae. The test characteristics of each formula (sensitivity, specificity and positive and negative predictive values) were determined against the reference standard. RESULTS: These results represent an interim analysis of our data. a total of 172 subjects were recruited, 39 of which delivered vaginally and 133 by caesarean section. after excluding cases with missing data, a total of 138 cases were analyzed. Of the four formulae identified to measure blood loss, two yielded meaningful results. A formula measuring percentage drop in hematocrit had a sensitivity of 73.1% and specificity of 31.4% for identifying PPH and another utilizing maternal height, body weight, and pre-and post-delivery hematocrit had a sensitivity of 44.0% and specificity of 77.9%. CONCLUSION: The study's interim analysis demonstrates that the use of formulae incorporating routinely determined variables such as pre- and post-delivery hematocrit, and/or body weight and height may be able to accurately and objectively identify cases of PPH and therefore have application in clinical and research settings.