## Core Concept
The question pertains to the leading cause of maternal mortality worldwide. Maternal mortality refers to the death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management (WHO). The causes can be broadly categorized into direct and indirect obstetric causes.

## Why the Correct Answer is Right
The most common cause of maternal mortality globally is postpartum hemorrhage (PPH), which accounts for approximately 28% of all maternal deaths. PPH is primarily caused by uterine atony, which is the failure of the uterus to contract after childbirth, leading to excessive bleeding. This condition can be due to various factors including overdistension of the uterus, prolonged labor, or retained placental tissue.

## Why Each Wrong Option is Incorrect
- **Option A:** While eclampsia is a significant cause of maternal and fetal morbidity and mortality, it is not the most common cause of maternal mortality. Eclampsia is a condition characterized by new-onset seizures in a pregnant woman with pre-eclampsia.
- **Option B:** Although infections (such as puerperal sepsis) are a critical cause of maternal mortality, especially in low-resource settings, they do not surpass postpartum hemorrhage as the leading cause.
- **Option C:** This option might refer to other causes such as obstructed labor or amniotic fluid embolism, which are serious but less common causes of maternal mortality compared to PPH.

## Clinical Pearl / High-Yield Fact
A crucial point to remember is the "4 Ts" for managing postpartum hemorrhage: Tone (uterine atony), Tissue (retained placental tissue), Trauma (lacerations), and Thrombin (coagulopathy). Early recognition and management of PPH, particularly by administering uterotonic agents like oxytocin, are critical in preventing maternal deaths.

## Correct Answer: D. Postpartum hemorrhage.