From the National Center for Health Statistics: Births: Provisional Data for 2017. The NCHS reports:
The provisional number of births for the United States in 2017 was 3,853,472, down 2% from 2016 and the lowest number in 30 years. The general fertility rate was 60.2 births per 1,000 women aged 15–44, down 3% from 2016 and another record low for the United States. …
Here is a long-term graph of annual U.S. births through 2017.
Births have declined for three consecutive years following increases in 2013 and 2014.
With fewer births and less net migration, demographics will not be as favorable as I was expecting a few years ago.