**Core Concept**
The Maternal Mortality Ratio (MMR) is a measure of the number of maternal deaths per 100,000 live births. It is an important indicator of the quality of healthcare services provided to women during pregnancy, childbirth, and the postpartum period.

**Why the Correct Answer is Right**
When MMR is expressed as 167, it means that for every 100,000 live births, 167 maternal deaths occurred. This ratio is calculated by dividing the number of maternal deaths by the number of live births, and then multiplying by 100,000 to express it as a rate per 100,000 live births. The correct denominator for MMR is indeed live births, as it reflects the number of women who gave birth and were at risk of maternal mortality.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to the calculation of MMR, which is a ratio of maternal deaths to live births, not a ratio of maternal deaths to total births.
**Option B:** This option is incorrect because MMR is calculated based on live births, not total births (which include stillbirths and other fetal losses).
**Option C:** This option is also incorrect because MMR is expressed as a rate per 100,000 live births, not per 10,000 total births.
**Option D:** This option is incorrect because MMR is a measure of maternal deaths among women who have given birth, not among all women of reproductive age.

**Clinical Pearl / High-Yield Fact**
To calculate MMR, you need to know the number of maternal deaths and the number of live births in a given population. A higher MMR indicates poorer maternal health outcomes and a greater need for improved healthcare services.

✓ Correct Answer: A. Per 100000 live births