Nicolaides et al developed an equation and nomogram for estimating the volume of donor blood required to transfuse in a fetus with erythroblastosis fetalis. The authors are from King's College Hospital in London.


(1) fetal hemoglobin

(2) donor blood hemoglobin (as packed red blood cells)

(3) adjusted fetoplacental blood volume based on week of gestation



• The equation for estimating the fetoplacental blood volume is described in Chapter 2.

• The donor hemoglobin is between 15 and 30 g/dL.

• The fetal hemoglobin is from 0 to 15 g/dL.


(fetal blood volume) / (donor blood volume) =

= (15 - (donor blood hemoglobin)) / ((fetal hemoglobin) - 15)



• 15 is the mean normal fetal hemoglobin value at 40 weeks gestation.


volume of donor blood to transfuse in mL =

= (fetoplacental blood volume in mL) / ((15 - (donor blood hemoglobin)) / ((fetal hemoglobin) - 15))



• Nicolaides provides a nomogram for a term "F". This is the inverse of ((15 - (donor blood hemoglobin)) / ((fetal hemoglobin) - 15)), which is multiplied by the fetal blood volume.

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