## **Core Concept**
Hemorrhagic disease of the newborn (HDN), also known as vitamin K deficiency bleeding (VKDB), is a bleeding disorder in newborns caused by a deficiency of vitamin K, which is essential for the production of clotting factors in the liver.

## **Why the Correct Answer is Right**
The correct answer, , is likely related to the characteristic presentation of HDN. Newborns with HDN often exhibit bleeding manifestations, which can range from mild to severe. A key feature of HDN is the occurrence of bleeding in the first few days of life, particularly in the first 24 hours. This condition is associated with **prolonged prothrombin time (PT) and activated partial thromboplastin time (aPTT)** due to the deficiency of vitamin K-dependent clotting factors (II, VII, IX, and X).

## **Why Each Wrong Option is Incorrect**
- **Option A:**
- **Option B:**
- **Option C:**

## **Clinical Pearl / High-Yield Fact**
A critical clinical pearl is that **vitamin K administration is a specific and effective treatment for HDN**. In fact, prophylactic vitamin K injection at birth is a standard practice in many countries to prevent HDN. Clinicians should be aware that breastfed infants, especially those who did not receive vitamin K prophylaxis at birth, are at higher risk for late-onset VKDB, which can present weeks after birth.

## **Correct Answer:** .