**Core Concept**
Postpartum women are at risk of developing a condition characterized by severe headache and visual changes due to an imbalance of blood vessels in the brain. This condition is caused by the sudden increase in intracranial pressure, which can lead to rupture of blood vessels and subsequent bleeding into the surrounding brain tissue.

**Why the Correct Answer is Right**
The most likely cause of this condition is postpartum intracerebral hemorrhage (ICH), specifically posterior communicating artery aneurysm rupture. The increased intracranial pressure can cause the aneurysm to rupture, leading to subarachnoid hemorrhage and subsequent bleeding into the surrounding brain tissue. This is often associated with sudden and severe headache, visual changes, and even loss of consciousness.

**Why Each Wrong Option is Incorrect**
**Option A:** Hypertension is a risk factor for intracerebral hemorrhage, but it is not the most likely cause of severe headache and visual changes in a postpartum woman.
**Option B:** Postpartum hemorrhage is a common complication of delivery, but it is not directly associated with severe headache and visual changes.
**Option C:** Migraine is a common headache disorder, but it does not typically cause visual changes or increased intracranial pressure.
**Option D:** Postpartum depression is a common condition, but it does not have a direct association with severe headache and visual changes.

**Clinical Pearl / High-Yield Fact**
Postpartum women with severe headache and visual changes should be immediately evaluated for subarachnoid hemorrhage or intracerebral hemorrhage, and prompt imaging studies such as CT or MRI should be performed to rule out these diagnoses.

**Correct Answer:** C. Migraine