A Kleihauer-Betke stain revealed 0.3% fetal cells in postpartum blood. What is the estimated volume of fetomaternal hemorrhage expressed as whole blood?

The Kleihauer-Betke stain is a test used to quantify fetal red blood cells present in maternal circulation, which can indicate the extent of fetomaternal hemorrhage. In this scenario, the stain shows 0.3% fetal cells in the postpartum maternal blood sample.

To calculate the estimated volume of fetomaternal hemorrhage, you can use the percentage of fetal cells detected in maternal blood. The formula for estimating the volume of the hemorrhage is:

Volume of fetomaternal hemorrhage = (Percentage of fetal cells in blood) x (Volume of maternal blood sampled).

Assuming the volume of maternal blood sampled is 100 mL, the calculation would be:

0.3% of 100 mL = 0.3 mL of fetal cells.

To estimate the total volume of fetal blood that corresponds to this percentage in the maternal circulation, you can apply the following relationship:

With a 0.3% representation, every 1% of fetal cells corresponds to an estimated total fetal blood volume of approximately 10 mL. Therefore, you would multiply the percentage by a factor of about 10 to convert this representation into an estimated volume of hemorrhage:

0.3% fetal cells x