Changing profile of births in the United States.
D000293:Adolescent; D000328:Adult; D001722:Birth Order; D001723:Birth Rate; D003466:Cultural Characteristics; D005191:Family Characteristics; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008423:Maternal Age; D008875:Middle Aged; D011247:Pregnancy; D014481:United States