**Core Concept**
Anti-D immunoglobulin is administered to RhD-negative women following delivery or abortion to prevent isoimmunization and potential hemolytic disease of the newborn. This is a crucial aspect of perinatal care, particularly in RhD-negative women who may be exposed to RhD-positive blood during pregnancy or childbirth.

**Why the Correct Answer is Right**
The American College of Obstetricians and Gynecologists (ACOG) recommends administering 300 micrograms of anti-D immunoglobulin within 72 hours of delivery to RhD-negative women who have delivered an RhD-positive fetus. This timing is critical to prevent sensitization and isoimmunization. The anti-D immunoglobulin works by neutralizing any fetal RhD-positive red blood cells that may have entered the maternal circulation, thereby preventing an immune response.

**Why Each Wrong Option is Incorrect**
**Option A:** Administering anti-D within 6 hours does not provide adequate protection against isoimmunization, as the risk of sensitization is still present beyond this timeframe.

**Option B:** Giving anti-D within 24 hours may not be sufficient to prevent sensitization, especially if the RhD-positive fetus has already released red blood cells into the maternal circulation.

**Option D:** Waiting 7 days to administer anti-D significantly increases the risk of sensitization and isoimmunization, as the maternal immune system may have already responded to the RhD-positive red blood cells.

**Clinical Pearl / High-Yield Fact**
To remember the timing of anti-D administration, the ACOG recommends using the "72-hour rule": Anti-D should be given within 72 hours of delivery to RhD-negative women who have delivered an RhD-positive fetus.

**✓ Correct Answer: C. 72 hours**