**Question:** In pregnancy, what is the dose of folic acid (in mcg/day)?

**Core Concept:** Folic acid is a B-complex vitamin essential for cell growth, DNA synthesis, and maintenance of healthy tissues. In pregnancy, folic acid supplementation plays a crucial role in preventing neural tube defects (NTDs) and other congenital anomalies.

**Why the Correct Answer is Right:** The correct answer is **D**: 400 mcg/day of folic acid is recommended during pregnancy. This dose is considered adequate to cover the increased demand for folic acid during pregnancy and to ensure proper fetal development.

**Why Each Wrong Option is Incorrect:**

A. **500 mcg/day (Option C)** is not sufficient to prevent NTDs as the optimal dose for prevention is usually considered to be higher than 400 mcg.

B. **200 mcg/day (Option D)** is lower than the recommended dose for optimal fetal development, making it insufficient.

C. **100 mcg/day (Option C)** is also lower than the recommended dose, making it inadequate for preventing NTDs and ensuring proper fetal development.

**Clinical Pearl:** Taking folic acid supplementation before and during the first trimester of pregnancy is essential for reducing the risk of congenital anomalies. Timely supplementation can lower the risk of NTDs by up to 70%.

**Correct Answer:** **D: 400 mcg/day** of folic acid is the correct dose for pregnant women to prevent neural tube defects and ensure optimal fetal development.