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    The principal investigators of the study request that you use the official version of the modified score here.

    Maternal-Fetal Hemorrhage Rh(D) Immune Globulin Dosage

    Calculates amount of RhIG to be administered to the mother, at the time of delivery, to prevent hemolytic disease of the fetus and newborn (HDFN).
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    IMPORTANT

    This dosing tool is intended to assist with calculation, not to provide comprehensive or definitive drug information. Always double-check dosing of any drug and consult a clinical pathologist or pharmacist when necessary.

    When to Use
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    Why Use

    This calculator should be used to compute the number of RhIG vials to administer to an Rh-negative mother who has not yet developed an anti-D, when she gives birth to an Rh-positive child.

    • Calculation of maternal blood volume is an estimation using Nadler’s equation.
    • Fetal cell percentage can be obtained by both flow cytometry or Kleihauer-Betke methodology.

    When a mother who is Rh-negative gives birth to a baby who is Rh-positive, there is a possibility that the mother could develop an antibody to the D antigen due to mixing of fetal and maternal blood. The presence of an anti-D leads to a potential risk for HDFN in future pregnancies. Therefore, to prevent HDFN and the formation of an anti-D in the mother, RhIG is given to the mother at 28 weeks and after birth. The amount of RhIG given to the mother after birth is dependent on the amount of fetal-maternal hemorrhage. This formula calculates the amount of fetal-maternal hemorrhage as well as the number of RhIG vials be given to the mother.

    mL
    %

    Result:

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    Next Steps
    Evidence

    Advice

    RhIG should be given to the mother at 28 weeks and after birth.

    Formula

    Number of RhIG vials = fetal cells/total cells counted × maternal blood volume, mL / 30 mL

    Then, round to the nearest whole number and add 1.

    Example:

    • Flow cytometry of fetal cells in maternal blood stream = 1.7%
    • Total maternal blood volume = 3,700 mL
    • Volume of fetal blood in maternal blood stream = 3,700 x 0.017 = 62.9 mL
    • Number of RhIG vials = 62.9 / 30 = 2.1 vials --> round down to 2 and add 1
    • RhIG vials to administer = 3 vials
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