Trends in "prematurity": United States, 1950-1967.
D000293:Adolescent; D000328:Adult; D001719:Birth Certificates; D001723:Birth Rate; D001724:Birth Weight; D036861:Delivery, Obstetric; D005006:Ethnicity; D005260:Female; D005865:Gestational Age; D006760:Hospitalization; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D007234:Infant, Premature; D008423:Maternal Age; D008875:Middle Aged; D012737:Sex Factors; D012959:Socioeconomic Factors; D014481:United States; D014798:Vital Statistics