Source: CDC National Center for Health Statistics
Latest Data: 2020
Frequency: Annual
Amounts: N/A
Contact: https://wwwn.cdc.gov/dcs/ContactUs/Form

According to the CDC, the Total Fertility Rate (TFR) estimates  "the number of births that a hypothetical group of 1,000 women would have over their lifetimes, based on age-specific birth rates in a given year. Because it is computed from age-specific birth rates, TFR is age-adjusted and can be compared for populations across time, population groups, and geographic areas.” The numerical value for TFR for a particular year is calculated by adding birth rates for five-year age groups multiplied by five.  A TFR of 1,723 per 1,000 women means that on average each woman has 1.7 children in her lifetime based on the current general birth rates for the different age groups. 

The Total Fertility Rate is also known as the replacement rate, the most important factor in population growth, and is generally considered to be 2,100 births per 1,000 women. This replacement rate is often given as 2.1 births per woman, which is what is needed to replace two individuals in the population.  In the United States the TFR has been mainly below replacement since 1971.

Source: National Vital Statistics Reports, Volume 72