Objective: The objective of the study was to compare visually estimated blood loss (vEBL) with calculated estimated blood loss (cEBL) according to mode of delivery and degree of perineal laceration.
Study design: Pre- and postdelivery hematocrit (HCT) and other variables including vEBL were prospectively recorded into an obstetrical database between January and September 2005. The cEBL was derived by multiplying the calculated pregnancy blood volume (0.75 x {[maternal height (inches) x 50] + [maternal weight in pounds x 25]}) by percent of blood volume lost ({predelivery HCT - postdelivery HCT}/predelivery HCT). cEBL and vEBL were compared according to mode of delivery and degree of perineal laceration.
Results: There were 677 subjects with complete data. vEBL was statistically different from cEBL between each degree of laceration and between all modes of delivery, demonstrating an underestimation of vEBL with increasing cEBL.
Conclusion: Improved methods for calculating blood loss include the use of a modified version of the formula used for pregnancy blood volume calculation.