Prophylactic anti-D immunoglobulin is given to Rh-negative pregnant women antenatally at
**Core Concept**
The administration of prophylactic anti-D immunoglobulin to Rh-negative pregnant women is based on the principle of preventing the formation of antibodies against Rh-positive fetal red blood cells, which can cross the placenta from the mother. This is crucial to prevent **hemolytic disease of the newborn** in future pregnancies. The timing of administration is key to its effectiveness.
**Why the Correct Answer is Right**
The correct timing for the administration of prophylactic anti-D immunoglobulin antenatally is typically around the 28th week of gestation. This timing is chosen because it is late enough in the pregnancy that the risk of sensitization has increased due to potential fetal-maternal hemorrhage but early enough that the immunoglobulin can effectively prevent the formation of anti-D antibodies for the remainder of the pregnancy.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because administering anti-D immunoglobulin too early may not provide protection for the entire pregnancy.
**Option B:** This option is not provided but would be incorrect if it suggested a time too late in pregnancy, as the goal is to prevent sensitization before it occurs.
**Option D:** Similarly, this option is not provided but would be incorrect if it suggested a time that does not align with standard clinical practice for the administration of anti-D immunoglobulin.
**Clinical Pearl / High-Yield Fact**
It's crucial to remember that anti-D immunoglobulin should also be administered within 72 hours of potential sensitizing events such as miscarriage, abortion, or any invasive prenatal diagnostic procedure to prevent isoimmunization.
**Correct Answer:** Correct Answer: C. 28 weeks of gestation.