National Center for Health Statistics

The U.S. fertility rate has declined 9% since the onset of the recession in 2007, with births declining every year. The decrease appears to have leveled off last year, a sign of an improved economy, though the change varied among age and race groups.
Sep 10, 2013   The New York Times - Health
The U.S. birth rate is now at the lowest recorded level ever - or at least since record-keeping began in 1920. Births were increasing but plunged after the 2007 recession. The biggest decrease is among immigrant groups, particularly Mexican women.
Dec 3, 2012   Pew Research Center