(July 2013) U.S. teen birth rates fell by 50 percent or more across all race and ethnic groups between 1991 and 2011, and the national teen birth rate is now at a record low, according to data recently released by the U.S. Centers for Disease Control and Prevention.

The birth rate for U.S. women ages 20 to 24 is also at an all-time low, while the birth rate for women ages 35 to 39 increased between 2010 and 2011 and the rate for women ages 40 to 44 has been slowly rising for more than two decades. Because of dramatically lower birth rates among women in their teens and 20s, the average age at first birth in U.S. continued to rise to 25.6 years in 2011, up from 25.4 in 2010 and 21.4 in 1970.

While birth rates have dropped sharply for young women, tracking trends in fertility for all women of reproductive age is more complex because of changes in the age structure of the population. To account for this, demographers rely upon the total fertility rate (TFR) to monitor trends over time. The TFR is the average number of births per woman. For example, a TFR of 2.0 means that women would have an average of two children each.

The TFR in 2011 was 1.89, down slightly from 1.93 in 2010, and considerably lower than the TFRs of 3.0 to 3.8 recorded during the baby boom in the 1950s. Nevertheless, the TFR for 2011 is higher than the record low (1.74) in 1976.

With respect to the health of babies born in 2011, there is good news. The preterm birth rate (children born at less than 37 weeks gestation) declined for the fifth straight year, and the rate of low birth weight (less than 5 lb. 8 oz.) births is also down from its peak in 2006.

Beth Jarosz is a research associate in Domestic Programs at PRB.