Background: Substantial development in social communication skills occurs in the first two years of life. Growth should be evident in sharing emotion and eye gaze; rate of communication, communicating for a variety of functions; using gestures, sounds and words; understanding language, and using functional and pretend actions with objects in play.…

Two-phase designs in epidemiological studies of autism prevalence introduce methodological complications that can severely limit the precision of resulting estimates. If the assumptions used to derive the prevalence estimate are invalid or if the uncertainty surrounding these assumptions is not properly accounted for in the statistical inference…