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Maternal-Fetal Hemorrhage Rh(D) Immune Globulin Dosage
Estimates the number of Rh(D) immune globulin vials needed after fetomaternal hemorrhage.
Maternal-Fetal Hemorrhage Rh(D) Immune Globulin Dosage
Fetal cells on Kleihauer-Betke stain (or equivalent flow cytometry)
%
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When to use
- Dosing Rh(D) immune globulin in an Rh(D)-negative mother after a sensitizing event (delivery, trauma, amniocentesis) once fetomaternal hemorrhage volume is quantified.
Formula
Fetal whole-blood volume (mL) = % fetal cells × 50 (assumes ~5000 mL maternal blood volume). Vials = round(volume / 30 mL) + 1 extra vial; each vial (300 mcg) neutralizes 30 mL fetal whole blood (15 mL fetal RBCs).
Pearls and pitfalls
- A standard 300-mcg dose is given regardless of calculation when the fetal bleed is not quantified or is below the threshold of one vial.
- For sensitizing events before 12 weeks' gestation, a 150-mcg mini-dose (covers 15 mL whole fetal blood) is generally adequate.