## **Core Concept**
The fetus requires a certain amount of iron for its growth and development throughout the pregnancy. Iron is crucial for the production of hemoglobin and various enzymes. The demand for iron increases during pregnancy to support both the mother's and the fetus's needs.

## **Why the Correct Answer is Right**
The fetus accumulates approximately **300 mg** of iron by the end of a full-term pregnancy. This iron is crucial for fetal hemoglobin production and for storage, which will be used during the early months of life. The fetal iron accumulation is an important consideration in maternal iron supplementation during pregnancy.

## **Why Each Wrong Option is Incorrect**
- **Option A:** 100 mg. This is lower than the actual amount required by the fetus.
- **Option B:** 500 mg. While maternal iron stores do increase during pregnancy, the fetus itself does not require this much iron.
- **Option D:** 1000 mg. This is significantly higher than the amount of iron the fetus needs to accumulate by the end of pregnancy.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the increased demand for iron during pregnancy is not just for the mother's expanded red blood cell mass but also for the fetus and placenta. Maternal iron deficiency can lead to fetal growth restriction and preterm labor, highlighting the importance of adequate maternal iron levels.

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