**Core Concept**
Hemorrhagic disease of the newborn (HDN) is a condition characterized by bleeding due to vitamin K deficiency in newborns. Vitamin K is essential for the synthesis of clotting factors in the liver, and its deficiency impairs the production of these factors, leading to bleeding.

**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of HDN. Newborns have low levels of vitamin K, which is necessary for the gamma-carboxylation of clotting factors, such as prothrombin and factors II, VII, IX, and X. This process is crucial for the activation of these clotting factors, and its deficiency leads to impaired blood coagulation and bleeding.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not describe a feature of HDN. Although hypoglycemia can occur in newborns, it is not a characteristic of HDN.

**Option B:** This option is incorrect because it is not a feature of HDN. Although thrombocytopenia can occur in various conditions, it is not specifically associated with HDN.

**Option C:** This option is incorrect because it does not accurately describe a feature of HDN. Although vitamin K deficiency can occur in newborns, it is not the only cause of bleeding in this population.

**Clinical Pearl / High-Yield Fact**
Newborns are at risk of vitamin K deficiency due to the lack of vitamin K in breast milk and the low levels of vitamin K in the mother's bloodstream. This highlights the importance of vitamin K prophylaxis in newborns to prevent HDN.

**Correct Answer: D.**