Macgregor et al used an equation to predict a fetal hematocrit some time after an intravascular intrauterine red blood cell transfusion. This can help determine if an additional transfusion may be required.


(1) hematocrit following the intrauterine transfusion

(2) fetal weight in grams at time of transfusion

(3) fetal weight in grams at followup

(4) number of days since transfusion


hematocrit predicted in percent =

= (hematocrit following transfusion) * (fetal weight at transfusion) / (fetal weight at followup) * (120 - (number of days since transfusion)) / 120



• 120 days reflects the lifespan of an erythrocyte.

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