**Core Concept**
The initiation of Antiretroviral Therapy (ART) in pregnancy is crucial for preventing mother-to-child transmission of HIV and maintaining the health of the mother.

**Why the Correct Answer is Right**
The World Health Organization recommends starting ART in all pregnant women living with HIV, regardless of their CD4 count or clinical symptoms. This is because ART not only reduces the viral load, thereby decreasing the risk of transmission to the baby, but also improves the health outcomes for the mother. The initiation of ART in pregnancy is guided by the principles of treating the mother, preventing mother-to-child transmission, and reducing the risk of HIV-related complications.

**Why Each Wrong Option is Incorrect**
**Option A:** This option may be incorrect because it does not consider the current guidelines for ART initiation in pregnancy, which recommend starting ART in all pregnant women living with HIV.

**Option B:** This option may be incorrect because it implies that ART should only be started in pregnancy when the mother's CD4 count is below a certain threshold, which is not in line with current recommendations.

**Option C:** This option may be incorrect because it does not account for the fact that ART is recommended for all pregnant women living with HIV, regardless of their CD4 count or clinical symptoms.

**Clinical Pearl / High-Yield Fact**
It is essential for healthcare providers to be aware of the current guidelines for ART initiation in pregnancy and to start ART in all pregnant women living with HIV, regardless of their CD4 count or clinical symptoms.

**Correct Answer:** D.