**Core Concept**
Preeclampsia is a pregnancy complication characterized by new-onset hypertension and proteinuria after 20 weeks of gestation. It can lead to severe maternal and fetal morbidity if not managed promptly.

**Why the Correct Answer is Right**
The most significant maternal complication and cause of death in preeclampsia is **cerebral hemorrhage**. This is due to the breakdown of the blood-brain barrier, leading to vasogenic edema and subsequent intracerebral hemorrhage. The pathophysiology involves endothelial dysfunction, increased vascular permeability, and coagulopathy. The severity of preeclampsia is often classified based on the presence of severe hypertension, proteinuria, and other complications like thrombocytopenia and renal failure.

**Why Each Wrong Option is Incorrect**
**Option A:** Eclampsia, which is the onset of seizures in a woman with preeclampsia, is a severe complication but not the most common cause of maternal death. While seizures can lead to significant morbidity, they are often managed with magnesium sulfate, reducing the risk of mortality.
**Option B:** Renal failure is a significant complication of preeclampsia but is not the leading cause of maternal death. While severe renal dysfunction can occur, it is often managed with dialysis and supportive care.
**Option C:** Placental abruption is a condition where the placenta separates from the uterus, leading to maternal and fetal distress. While it is a serious complication, it is not the most common cause of maternal death in preeclampsia.

**Clinical Pearl / High-Yield Fact**
It is essential to recognize that preeclampsia can be a catastrophic condition if not managed promptly. Early recognition of symptoms, such as severe hypertension, proteinuria, and visual disturbances, is crucial in preventing complications like cerebral hemorrhage.

**Correct Answer:** C.