In 2000, 467,201 of the 4,058,814 babies born in the United States were preterm and 307,030 were born low birthweight.  This means 11.6 percent of live births were born too early, or prior to the 37th week of pregnancy, and 7.6 percent were born too small, weighing less than 2500 grams or 5 1/2 pounds.