Civil registry figures show that births in the first seven months of the current Iranian year fell 9.9% compared to the previous year, Tasnim's Persian-language site reported.
The Friday report cites civil registry figures showing that Tehran Province recorded 58,355 births in the first seven months of the current Iranian year, down 9.9% from 64,771 in the same period a year earlier.
At the same time, deaths rose by more than 6%, from 37,282 to 39,588.
As a result, natural population growth, the difference between births and deaths, fell by nearly 32%, from about 27,500 to fewer than 19,000.
Tasnim cited social experts who pointed to rising living costs, housing difficulties, and broader economic pressures as factors discouraging people from having children. The site also linked the rise in deaths to an aging population and called for an urgent review of existing population policies.