Discrepancy between laboratory determination and visual estimation of blood loss during normal delivery.

Blood loss during normal delivery was measured in 37 primiparas and 25 multiparas who had no obstetric or medical complications and who underwent normal delivery in a teaching hospital following spontaneous onset of labour at term. Measured blood loss was significantly greater than the estimated volume of blood loss. In primigravidas, the mean ( +/- SE, standard error of the mean) estimated blood loss was 260 +/- 12 ml and the mean measured blood loss was 401 +/- 29 ml. In multiparas the mean estimated blood loss was 220 +/- 10 ml and the mean measured blood loss was 319 +/- 41 ml. The mean estimated blood loss was significantly lower (P less than 0.05) than the mean measured blood loss in both groups. The size of the discrepancy between measured and estimated blood loss was proportional to the measured blood loss. These findings show that visual estimation of blood loss was grossly inaccurate.