192,059 TRENDS Trends in "Prematurity". United States: 1950-67.An analysis of the trend in live births registered in the United States, 1950-67 by weight at birth and period of gestation,including an assessment of the quality of the data.... Rockville 1972 U. S. Department of Health, Education,and Welfare,Public Helalth Service 4° s. IV, 51, ilustr. Vital and Health Statistics.Analytical Studies.Ser.3 Nr 15.