**Core Concept**
Anti-D immunoglobulin is administered to non-immune Rh D negative women to prevent the formation of anti-D antibodies against Rh D positive red blood cells, which can occur during pregnancy or childbirth. This is a crucial measure to prevent hemolytic disease of the newborn (HDN) in future pregnancies.

**Why the Correct Answer is Right**
The dose of anti-D immunoglobulin recommended for non-immune Rh D negative women after delivery is 300 mg. This dose is sufficient to cover the potential exposure to Rh D positive fetal red blood cells during delivery, thereby preventing the sensitization of the mother's immune system. The administration of anti-D immunoglobulin is typically given within 72 hours of delivery to ensure optimal efficacy.

**Why Each Wrong Option is Incorrect**
**Option A:** 50 mg is an insufficient dose to prevent sensitization, as it may not provide adequate coverage against the exposure to Rh D positive red blood cells during delivery.
**Option B:** 150 mg is still below the recommended dose, and its efficacy in preventing sensitization is uncertain.
**Option D:** 450 mg is excessively high and not recommended for routine use in non-immune Rh D negative women after delivery.

**Clinical Pearl / High-Yield Fact**
It is essential to administer anti-D immunoglobulin within 72 hours of delivery to ensure optimal efficacy in preventing sensitization. This time frame is critical in preventing the formation of anti-D antibodies against Rh D positive red blood cells.

**Correct Answer:**
✓ Correct Answer: C. 300 mg.