childbearing..
By definition, replacement is only considered to have occurred when the offspring reach 15 years of age. If there were no mortality in the female population until the end of the childbearing years (generally taken as 44 or 49, though some exceptions exist) then the replacement rate would be exactly 2, but in practice it is affected by mortality, especially childhood mortality.
but if fertility rate is constant, and the death rate after childbearing is decreasing overtime, then the population (people alive) is growing. Common Sense.