A working paper published by the National Bureau of Economic Research (NBER) in 2026 highlights that the total fertility rate in the United States has plummeted by 22% since 2007. This downward trend cannot be entirely attributed to conventional factors like economic conditions, the widespread availability of contraception, housing expenses, or the stress associated with parenting. The research team then redirected their attention to the rapid spread of smartphones, with a particular focus on the launch of the original iPhone. By scrutinizing AT&T base station coverage data, they discovered that from 2007 to 2011, areas with a high prevalence of iPhones experienced a 4.5%-8% drop in fertility rates among women aged 15-24. In contrast, the impact on women over 30 was relatively minor. Further research on a global scale suggests that the timing of accelerated fertility declines in 128 countries closely corresponds with the moment when smartphone sales exceeded critical thresholds. Variations in 4G coverage due to natural conditions, such as rugged terrain, also underscore the substantial influence of digital infrastructure on the reproductive behavior of adolescents. The paper points out that smartphones influence fertility decisions through various mechanisms, including the reshaping of social patterns, the provision of immediate entertainment alternatives, and the reduction of the risk of unintended pregnancies. While economic pressures continue to be a fundamental factor, the penetration of technology has intensified its suppressive effect on fertility rates.