**Core Concept**
Pre-eclampsia is a pregnancy complication characterized by high blood pressure and damage to organs such as the liver and kidneys. It is a leading cause of maternal and fetal morbidity worldwide. The underlying pathophysiological mechanism involves abnormal placentation and endothelial dysfunction.

**Why the Correct Answer is Right**
Chronic hypertension is a well-established risk factor for the development of pre-eclampsia. Women with a history of chronic hypertension are at an increased risk of developing pre-eclampsia due to the underlying endothelial dysfunction and vascular remodeling. This predisposes them to develop high blood pressure and proteinuria during pregnancy. The renin-angiotensin-aldosterone system (RAAS) plays a crucial role in the pathogenesis of pre-eclampsia, and women with chronic hypertension have an altered RAAS activity.

**Why Each Wrong Option is Incorrect**
**Option A:** Diabetes mellitus is a risk factor for pre-eclampsia, but it is not the greatest risk factor. Women with diabetes are at an increased risk of developing pre-eclampsia due to the underlying vascular dysfunction and inflammation.
**Option B:** Multiple gestations are a risk factor for pre-eclampsia, but they are not the greatest risk factor. Women carrying twins or other multiple gestations are at an increased risk of developing pre-eclampsia due to the increased placental mass and vascular resistance.
**Option C:** Nulliparity is a risk factor for pre-eclampsia, but it is not the greatest risk factor. Women who are pregnant for the first time are at an increased risk of developing pre-eclampsia due to the underlying endothelial dysfunction and abnormal placentation.

**Clinical Pearl / High-Yield Fact**
The risk of pre-eclampsia is highest in women with a history of chronic hypertension, especially those with a history of preeclampsia in a previous pregnancy. This is a classic exam trap, and students should remember that chronic hypertension is the greatest risk factor for pre-eclampsia.

**Correct Answer:** C. Nulliparity is a risk factor for pre-eclampsia, but it is not the greatest risk factor. Women who are pregnant for the first time are at an increased risk of developing pre-eclampsia due to the underlying endothelial dysfunction and abnormal placentation.