**Core Concept**
Maternal mortality rate (MMR) is a public health indicator that measures the number of maternal deaths per 100,000 live births. It reflects the risk of death during pregnancy, childbirth, or within 42 days postpartum, and is used to assess maternal healthcare access and quality.

**Why the Correct Answer is Right**
The standard definition of maternal mortality rate is calculated as the number of maternal deaths per 100,000 live births. This standardization allows for accurate comparison across populations and regions. The World Health Organization (WHO) and the United Nations define MMR using this formula, ensuring consistency in global health reporting.

**Why Each Wrong Option is Incorrect**
Option B: "Maternal death /100 live bihs" is incorrect because it lacks the standard denominator (100,000) and is not the WHO-recommended definition.
Option C: "Maternal death /1000 bihs" is too high a denominator and does not align with global standards.
Option D: "Maternal death /1000 live bihs" is an outdated or regional estimate and not the internationally accepted metric.

**Clinical Pearl / High-Yield Fact**
Always remember: MMR = maternal deaths per 100,000 live births. This is the only formula accepted by WHO and used in global health assessments. Avoid using per 100 or per 1000 — it’s a common exam trap.

**✓ Correct Answer: A. Maternal deaths / 100000 live bihs**