Total fertility rate (children per woman) has been below 2 since the 70s. We still have natural growth, but that's because of age distributions, not fertility ( (if you have a lot of 30 year old women, your birthrate will be very high even if they only have one each... vs a population of 60 year old women, who also had one each but are not presently childbearing), compounded by the fact that until recently we had a relatively small number of old people dying.  

Our natural growth rate (births minus deaths) will become negative once the Millennial bulge starts reaching the end of their reproductive years in about a decade reducing births, which will also coincide with the Boomers starting to reach their 80s and beginning to die in large numbers . 

There are no subsequent "bulges" after that, so even if total fertility rate doubles to 3, there simply won't be enough women of childbearing age to push crude birthrates up again.