Since the start of the recession, the birth rate in America has been declining.  Last year it plunged to its lowest level since at least 1920. That's according to a study released by the Pew Research Center. The overall birth rate in 2011 was 63-point-2 per one thousand women of childbearing age. The biggest dip in recent years is among immigrant women. The number of foreign-born women having babies dropped 14-percent between 2007 and 2010. Among women from Mexico, the birth rate fell by 23-percent. The birth rate for U-S born women declined 6-percent in that same period.