In this article, the changes of the fertility of women in the family from 1981 to 2011 have been analyzed by using demographic documents or the secondary analysis of statistics. According to available statistics, the annual growth rate of Iran's population in 1986 was reported at 3. 9%, which fell to 1. 3% in 2011. In such a situation, the number of households expected to grow in line with the decline in population growth, while statistical evidence suggests that the annual growth rate of households in the 1996-86 period was only 2. 51% that is up by 3. 89 percent compared to 2011. During these three decades, household households also respectively dropped from 5. 11 to 4. 05 and 3. 54. The theoretical analysis of such a situation, based on the theory of the transition of the second population, indicates the introduction of the values of modernism and its manifestations (individualism, industrialization and urbanization), such as the single parent, single child, biological couple, and the same as the growth of the divorce phenomenon. According to this theory, the findings of the present study indicate that households with a population of 7 people are now fading with a 2% share of the total population, the growth rate of 3 to 4-person households, accounting for half of Iran's population, is also decreasing and rising to 7% in single-person households. According to these findings, it can be concluded that during the last three decades, the reduction of fertility preference, the desire for single life and the formation of independent pre-marital households, along with a further factor called divorce, has reduced household size and increased the number of households. It shows the arrival of the values of modernism in the realm of Iranian homeland.