**Question:** Anti-D immune globulin is administered to Rh-negative women antenatally at

A. 28 weeks
B. 24-28 weeks
C. 26 weeks
D. 20 weeks

**Correct Answer:** .

**Core Concept:**
Anti-D immune globulin is a type of immunoglobulin G (IgG) used to prevent Rh sensitization in pregnant Rh-negative women. It is administered when there is a risk of Rh-positive blood coming into contact with the Rh-negative blood, as this can lead to the production of anti-D antibodies in the Rh-negative woman, potentially causing hemolytic disease of the fetus and newborn (HDFN).

**Why the Correct Answer is Right:**
Anti-D immune globulin is given antenatally (during pregnancy) at a specific time to maximize its effectiveness in preventing Rh sensitization. The correct answer (B) suggests administering the drug between 24-28 weeks, which is the optimal time window when the risk of Rh sensitization is highest due to fetal Rh-positive organogenesis and placental function.

**Why Each Wrong Option is Incorrect:**
A. 28 weeks (Option A): This is too late in the pregnancy, and the drug may not have enough time to effectively neutralize anti-D antibodies before they are produced.
C. 26 weeks (Option C): While this is earlier than Option A, it is still close to term and the risk of sensitization may be lower.
D. 20 weeks (Option D): This is too early in the pregnancy, and the drug may not be as effective due to incomplete fetal organogenesis and immature placental function.

**Why Option B is Right:**
Option B (24-28 weeks) is the optimal time for administering anti-D immune globulin due to the increased risk of Rh sensitization during this period. The drug can effectively neutralize anti-D antibodies before they cause sensitization and subsequent hemolysis in the fetus or newborn.

**Clinical Pearl:**
In cases of Rh incompatibility, it is essential to administer anti-D immune globulin during the second trimester to ensure the drug reaches the maternal bloodstream before anti-D antibodies are produced. Early intervention reduces the risk of HDFN (hemolytic disease of the fetus and newborn) and is crucial for the wellbeing of the fetus and newborn.