Americans had fewer babies in 2011 than in any year before, according to an annual summary of vital statistics.

-Johns Hopkins Bloomberg School of Public Health in Baltimore

That number, combined with population data, yielded a crude birth rate of 12.7 per 1,000 people, the lowest rate ever reported for the nation, they reported online and in the March 2013 issue of Pediatrics.

he general fertility rate — defined as the number of births per 1,000 women ages 15 through 44 — also fell by 1 percent, to a record low of 63.2 in 2011, down from 64.1 in 2010.

But the declines were not uniform according to age, the authors pointed out.

The birth rate among all teenagers (ages 15-19) fell by 8 percent from 2010 to 2011, reaching a historic low of 31.3 births per 1,000 women. That rate has been falling for years, Hamilton and colleagues noted and is down 49 percent from 1991, the most recent peak.