**Core Concept**
Perinatal mortality refers to the number of deaths occurring in the perinatal period, which is defined as the period between 22 weeks of gestation and 7 days after birth. It is an important indicator of maternal and child health, reflecting the quality of obstetric care and the overall well-being of the population.

**Why the Correct Answer is Right**
Perinatal mortality rate (PMR) is expressed as the number of deaths per 1,000 live births. This is because live births are the denominator, and the numerator is the number of deaths that occurred in the perinatal period. The use of live births as the denominator helps to standardize the rate and make it more comparable across different populations. It also takes into account the fact that not all pregnancies result in live births, and the rate would be skewed if total births (live and stillbirths) were used as the denominator.

**Why Each Wrong Option is Incorrect**
**Option A:** Deaths/1000 total births is incorrect because it includes stillbirths, which are not part of the perinatal mortality rate. The perinatal mortality rate specifically refers to deaths occurring after 22 weeks of gestation, making stillbirths irrelevant.
**Option C:** Deaths/10000 total births is incorrect because it uses an incorrect denominator (total births instead of live births) and an incorrect unit (10,000 instead of 1,000).
**Option D:** Deaths/10000 live births is incorrect because it uses an incorrect unit (10,000 instead of 1,000).

**Clinical Pearl / High-Yield Fact**
The perinatal mortality rate is a key indicator of the quality of obstetric care and the overall health of the population. It is influenced by factors such as access to prenatal care, maternal education, and the availability of emergency obstetric services.

**Correct Answer:**
✓ Correct Answer: B. Deaths/1000 live births