## **Core Concept**
The administration of anti-D gamma globulin (also known as RhoGAM) is a critical practice in obstetrics to prevent the sensitization of Rh-negative mothers to Rh-positive fetal blood cells. This is particularly important in cases where an Rh-negative mother delivers an Rh-positive baby, as it prevents the formation of antibodies against Rh-positive blood, which could complicate future pregnancies.

## **Why the Correct Answer is Right**
The standard dose of anti-D gamma globulin given postpartum for this purpose is **300 micrograms**. This dose is sufficient to neutralize the fetal-maternal hemorrhage that typically occurs during delivery. The anti-D gamma globulin works by binding to any Rh-positive red blood cells that may have entered the mother's circulation, marking them for destruction and preventing an immune response against them.

## **Why Each Wrong Option is Incorrect**
- **Option A:** 100 micrograms - This dose is lower than the standard dose given postpartum and would likely be insufficient to neutralize the amount of Rh-positive blood that could enter the mother's circulation during delivery.
- **Option B:** 200 micrograms - While closer to the standard dose, it is still less than the commonly recommended dose for postpartum administration.
- **Option D:** 50 micrograms - This dose is significantly lower than the standard and would not provide adequate protection against sensitization.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the dose of anti-D gamma globulin may vary depending on the clinical scenario, such as the dose given antenatally (usually 50 micrograms) being different from the postpartum dose. However, for postpartum administration to an Rh-negative mother who has just delivered an Rh-positive baby, **300 micrograms** is the standard dose.

## **Correct Answer:** D. 300 microgm