The number of pregnant women expected in a population is calculated using:

Here:

Calculation: = (30 / 1000) × 5,000 = 150 pregnant women

This is a standard community medicine formula used to estimate the expected number of antenatal cases registered under a subcenter. At a birth rate of 30/1000, a population of 5,000 would yield 150 births per year, meaning 150 pregnant women at any given time (assuming each pregnancy results in one birth and all are registered).