**Core Concept**
Iron is a crucial micronutrient for fetal growth and development during pregnancy. The demand for iron increases significantly due to the expansion of maternal blood volume, increased oxygen delivery to the fetus, and the production of red blood cells.

**Why the Correct Answer is Right**
The recommended daily iron intake during pregnancy is approximately 1,000-1,300 mg. This increased demand is met by a combination of dietary sources and iron supplementation. The body absorbs iron from the gut in the form of ferrous iron, which is then transported to the bone marrow for erythropoiesis. The requirement for iron is highest during the second and third trimesters, making regular iron supplementation essential to prevent iron deficiency anemia.

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect as it does not account for the significant increase in iron requirement during pregnancy. The recommended daily intake is higher than the standard non-pregnant requirement.

**Option B:**
This option is incorrect as it is lower than the recommended daily intake during pregnancy. Iron deficiency anemia is a common complication of pregnancy, and inadequate iron supplementation can exacerbate this condition.

**Option C:**
This option is incorrect as it is based on a non-pregnant requirement. The body's demand for iron increases significantly during pregnancy, necessitating a higher intake.

**Clinical Pearl / High-Yield Fact**
Regular iron supplementation is essential during pregnancy to prevent iron deficiency anemia, which can lead to complications such as preterm labor, low birth weight, and maternal morbidity.

**Correct Answer: D. 1,000-1,300 mg.**