This study explores a novel channel for monetary policy to impact growth and welfare—through fertility choice. In a scale-invariant Schumpeterian growth model with endogenous fertility and a cash-in-advance constraint on consumption, we find a positive effect of an increase in the nominal interest rate on fertility. The increase in fertility decreases labor supplied to production and R&D, which in turn decreases long-run growth. Calibration shows that long-run growth increases 0.12% by reducing the nominal interest rate from 9.6% to 0%, and the welfare gain is equivalent to a permanent increase in consumption of 3.14%. As an empirical test, we build panel data for 12 advanced countries during 2000–2014. We use the degree of central bank independence and money growth as the instruments for inflation. We find that the effect of inflation on population growth is positive and significant in instrumental variables estimation. Our results remain robust to using birth rate or fertility rate as the dependent variable. An increase in annual inflation of 1 percentage point would bring an increase of 0.06 percentage point in the annual growth of the total population. Our empirical findings provide support for our theory.