## **Core Concept**
The maternal mortality rate (MMR) is a critical indicator used to assess the quality of healthcare in a country, particularly in relation to pregnancy and childbirth. It measures the number of deaths occurring among women due to complications of pregnancy or childbirth. Understanding the denominator of MMR is essential for accurately calculating and interpreting this statistic.

## **Why the Correct Answer is Right**
The correct denominator for calculating the maternal mortality rate (MMR) is **live births**. MMR is specifically defined as the number of maternal deaths per 100,000 live births. This means that for every 100,000 live births, the number of maternal deaths that occur is counted and expressed as a rate. Using live births as the denominator allows for a standardized measurement that reflects the risk of maternal mortality associated with childbirth.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Deaths due to pregnancy-related causes are part of the numerator in MMR, not the denominator.
- **Option B:** Maternal deaths per 100,000 population is actually the definition of maternal mortality ratio when the population is specified, but it's not the standard denominator used for MMR.
- **Option C:** This seems to relate to the numerator or an alternate expression of MMR rather than specifying a denominator.
- **Option D:** While maternal deaths are a component of MMR, they represent what is being counted (the numerator), not the denominator.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that MMR is expressed per 100,000 live births. This highlights the importance of accurate registration of both maternal deaths and live births to compute a reliable MMR. A high MMR indicates a higher risk of death for women related to pregnancy and childbirth, reflecting potential gaps in healthcare quality.

## **Correct Answer:** B. live births.