title: The issue of sample characteristics: biologically at risk or developmentally delayed infants.
mesh_terms: D000367:Age Factors; D002658:Developmental Disabilities / Q000523:psychology*; D004314:Down Syndrome / Q000523:psychology; D006304:Health Status; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D008607:Intellectual Disability / Q000523:psychology; D012107:Research Design; D012306:Risk; D012494:Sampling Studies