[Mean length utterance (MLU) as a measure of language development of children with Down syndrome].

Purpose: To characterize the mean length utterance in morphemes (MLU-m) and words (MLU-w) produced by children with Down syndrome (DS), and to verify the effectiveness of using EME-w as a measure of general language development of children with DS.

Methods: Participants were 15 children with ages between 5 and 12 years, who were submitted to a free interaction situation. They were divided into three groups, according to chronological and mental age, as established by the results of the Primary Test of Nonverbal Intelligence. The first 100 utterances were analyzed considering: number of grammatical morphemes (GM) for articles, nouns and verbs (GM-1), and pronouns, prepositions and conjunctions (GM-2); mean length utterance for morphemes (MLU-m) and words (MLU-w).

Results: The between-groups comparison showed that the MLU averages were higher for older groups, and differences were found for all variables, except for GM-2. The same results were obtained in the within-group comparison, for all variables. There was a strong correlation between MLU-m and MLU-w.

Conclusion: MLU-w can be used as an identification measure of general linguistic development. However, it is emphasized that the use of all MLU variables provides more efficacy in the characterization of linguistic development and the analysis of language impairments.