**Core Concept**
The question involves calculating the number of pregnant women in a given population based on the birth rate. The **birth rate** is the number of live births per 1,000 people in a population per year.

**Why the Correct Answer is Right**
To find the number of pregnant women, we can estimate that the birth rate reflects the number of pregnancies resulting in live births. Given a birth rate of 30 per thousand and a population of 5,000, we calculate the expected number of births as 30/1,000 * 5,000 = 150. Assuming each pregnant woman gives birth, the number of pregnant women would be approximately equal to the number of expected births.

**Why Each Wrong Option is Incorrect**
**Option A:** This option would be incorrect because it does not accurately reflect the calculation based on the given birth rate and population size.
**Option B:** Similarly, this option is incorrect as it does not match the expected number of pregnancies based on the provided birth rate.
**Option C:** This option is also incorrect because it does not align with the calculated number of pregnant women based on the birth rate and population.

**Clinical Pearl / High-Yield Fact**
Remember, the **birth rate** is a key indicator of population growth and health status. In calculations like these, it's essential to understand the relationship between birth rates, population size, and the number of pregnant women.

**Correct Answer:** B. 150