Obstetrics
Anti-D Immune Globulin (RhoGAM) Dosing & Kleihauer-Betke FMH Calculator
Calculates fetal-maternal hemorrhage (FMH) volume and ACOG-recommended 300 mcg RhoGAM vials.
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Parameters
Anti-D Immune Globulin (RhoGAM) Dosing & Kleihauer-Betke FMH Calculator Result
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Formula
Fetal Whole Blood (mL) = (% Fetal RBCs in KB ÷ 100) × Maternal Blood Volume (mL)
Raw Vials = Fetal Whole Blood (mL) ÷ 30 mL
ACOG Rounding = Decimal < 0.5 → Round Down + 1 | Decimal ≥ 0.5 → Round Up + 1Clinical Pearls
Prevents hemolytic disease of the fetus and newborn (HDFN / erythroblastosis fetalis) in subsequent pregnancies by eliminating circulating fetal Rh+ D antigens.
Limitations
Maternal hemoglobinopathies with elevated Hemoglobin F (e.g., Hereditary Persistence of Fetal Hemoglobin [HPFH], Beta-Thalassemia minor) can falsely elevate KB counts; flow cytometry with anti-HbF/anti-D is diagnostic.