<p>Early detection and characterization of autism spectrum disorder (ASD) may be improved by incorporating ecologically valid methods into ASD screening and assessment, capitalizing on prospective monitoring of high-risk populations, and targeting highly informative ASD features that emerge early in development. The present study aims to address these barriers by characterizing early vocal and pre-linguistic communication features present during naturalistic behavior samples of young children with neurogenetic syndromes (NGS). Participants were 39 children aged 5-30 months diagnosed with an NGS and 39 children aged 4-26 months at low risk for developmental delays. Participants completed a daylong audio recording of child vocalizations from which measures of early vocal features (child vocalization rate, canonical babbling ratio, and pitch variability) were obtained. Participants and their mothers also completed an unstructured play-based task during which pre-linguistic communicative features (communication complexity and function) were coded. We first used Bayesian analyses to compare the early vocal and pre-linguistic communication features of children with NGS to those of children at low risk for developmental delays. Children with NGS used less canonical babble, lower communication complexity overall and for behaviors for the purposes of joint attention. Next, we conducted a cluster analysis of early vocal and pre-linguistic communication features using the full sample of NGS and low-risk participants. The selected model identified 6 clusters that were primarily differentiated by canonical babbling and communicative function. These clusters differentiated participants beyond risk status, chronological age and adaptive age. Furthermore, certain clusters reflected differences in adaptive communication and socialization skills that may be relevant to early ASD profiles. These findings suggest that canonical babble and communicative function provide meaningful information about early developmental risk and may be useful to incorporate into the ASD screening and diagnostic processes.</p>