A 14-week Rh-negative pregnant woman presents with mild vaginal bleeding and abdominal pain. Ultrasound shows a viable intrauterine pregnancy. Her husband is Rh-positive. What dose of Anti-D immunoglobulin should be administered?

1. A

   50 mcg

2. B

   75 mcg

3. C

   100 mcg

4. D

   150 mcg

Appeared in: NORCET-7 Mains-2024

Explanation

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• The patient is at 14 weeks gestation and has experienced vaginal bleeding, which is a potential sensitizing event where fetal Rh-positive red blood cells can enter the maternal circulation.
• To prevent the mother from developing antibodies against the Rh-D antigen (Rh isoimmunization), administration of Anti-D immunoglobulin is necessary.
• Standard guidelines recommend a dose of 50 mcg (equivalent to 250 IU) for sensitizing events that occur in the first and early second trimester (up to 20 weeks of gestation).
• This smaller dose is sufficient because the total fetal blood volume at this stage is low, and any potential fetomaternal hemorrhage would be small.

Why Other Options Were Wrong

• Option B: This is not a standard recommended dose for Anti-D immunoglobulin in any established clinical protocol for Rh prophylaxis.
• Option C: A dose of 100 mcg (or 125 mcg, equivalent to 500-625 IU) is the minimum recommended dose for sensitizing events that occur after 20 weeks of gestation.
• Option D: This is not a standard dose. The full prophylactic dose administered routinely at 28 weeks or postpartum is typically 300 mcg (1500 IU).

Related Visual

• Visual 1: Diagram illustrating the mechanism of Rh isoimmunization, showing an Rh-negative mother and an Rh-positive fetus, with fetal red cells crossing the placenta.
• Visual 2: Chart showing the recommended Anti-D immunoglobulin dosage based on gestational age and the type of sensitizing event (e.g., threatened abortion, amniocentesis, delivery).

Clinical Relevance

• Nursing practice connection: Use the key finding related to Anti-D immunoglobulin (RhoGAM) dosing for Rh isoimmunization prophylaxis during pregnancy to guide bedside assessment, documentation, and the next nursing action.
• Administering the correct dose of Anti-D immunoglobulin within 72 hours of a sensitizing event is critical to prevent maternal antibody formation. This protects future pregnancies from Hemolytic Disease of the Fetus and Newborn (HDFN), a condition that can cause severe fetal anemia, hydrops fetalis, and death.
• Nurses play a key role in verifying the patient's blood type, Rh factor, and antibody screen (indirect Coombs' test) before administering Anti-D to ensure she is Rh-negative and not already sensitized.
• Patient education is crucial. The nurse should explain why the injection is needed, its benefits for future pregnancies, and potential side effects.

How to Approach the Question

• First, identify the key clinical details from the scenario: the mother is Rh-negative, the gestational age is 14 weeks, and a sensitizing event (vaginal bleeding) has occurred.
• Recall the purpose of Anti-D immunoglobulin: to prevent the mother from developing antibodies against Rh-positive fetal blood, which could harm future pregnancies.
• Access your knowledge of the standard dosing protocols for Anti-D immunoglobulin, which are tiered based on gestational age.
• Compare the patient's gestational age (14 weeks) to the established dosing periods. The period for early pregnancy sensitizing events (up to 20 weeks) requires a specific dose.
• Evaluate the options provided. Select the option that matches the recommended dose for a sensitizing event in the early second trimester.
• Eliminate doses that are non-standard (75 mcg, 150 mcg) or used for later gestational ages (100 mcg).

Concept Tested & Keywords

• Concept Tested: Anti-D immunoglobulin (RhoGAM) dosing for Rh isoimmunization prophylaxis during pregnancy.
• Stem keywords: 14-week, Rh-negative, pregnant, vaginal bleeding, Rh-positive husband, Anti-D immunoglobulin
• Lead-in keywords: What dose
• Clinical cues: Gestational age of 14 weeks places the patient in the early second trimester.
• Clinical cues: Vaginal bleeding is a potential sensitizing event requiring prophylaxis.

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