**Core Concept**
The scenario presents a mother with active tuberculosis (TB) who has just delivered a baby. The primary concern is the transmission of TB to the newborn, highlighting the need for appropriate post-exposure prophylaxis.

**Why the Correct Answer is Right**
In cases of active TB exposure, particularly in a mother who has just delivered, the risk of transmission to the newborn is significant. The World Health Organization (WHO) recommends isoniazid (INH) prophylaxis for the infant as a precautionary measure. This is because the infant is at a higher risk of developing TB due to the immature immune system and the possibility of transmission through the birth canal. The administration of INH for 6 months is a standard practice to prevent the development of TB in the newborn.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant in the context of TB prophylaxis in a newborn.
**Option B:** This option does not provide any specific guidance on TB prophylaxis in a newborn.
**Option C:** This option is incorrect as it does not address the specific scenario of a mother with active TB delivering a baby.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the BCG vaccine, commonly administered in countries with high TB prevalence, does not provide adequate protection against pulmonary TB and does not prevent the transmission of TB from an infected mother to her newborn.

**Correct Answer:** D.