Postural Development in Infants with and without Risk for Autism Spectrum Disorders

Background: Evidence suggests that motor impairments exist in children and adults diagnosed with autism spectrum disorders (ASD), including difficulties with postural stability. Retrospective video studies of infants later diagnosed with ASD indicate that these atypicalities may be apparent early in development (e.g., Ozonoff, 2007). Delays and/or atypicalities in postural development may thus be potential indicators of risk for an eventual ASD diagnosis.

Objectives: The goal of this study is to investigate early postural development prospectively and longitudinally in infants at heightened risk for ASD and comparison infants in a naturalistic setting.

Methods: Twenty-one infants (6 male) with an older sibling diagnosed with autism (High Risk; HR) and 18 infants (8 male) with a typically-developing older sibling (Low Risk; LR) participated in this research. At 36 months, the ADOS-G (Lord et al., 2000) was administered to all HR infants; three received an autism diagnosis (AD infants).   Infants were videotaped at home for approximately 45 minutes at 6, 9, 12, and 14 months while engaged in everyday activities and play.  All postures were coded (i.e., Prone, Supine, Sit Supported), and each posture change was characterized as being initiated by either the child or parent. All supported postures were further classified according to source of sustainment (i.e., child, parent, other).  

Results: HR and LR infants exhibited comparable postural behavior. With age, they spent less time in postures involving external sources of support (e.g. Prone) and more time in postures requiring increased strength and balance (e.g. Stand Unsupported).  AD infants, however, were observed in a smaller variety of postures, and the emergence of more advanced self-initiated postures was substantially delayed.  
At each age point, AD infants had fewer postures in their repertoire.  For example, at 9 months, AD infants were only observed in Prone, Supine, and All-4 postures.  HR and LR infants exhibited postures similar to the AD infants, but were also observed in Sit Supported, Sit Unsupported, Kneel, and Stand Supported.  
AD infants initiated posture changes later than HR and LR infants.  For example, HR and LR infants were seen moving themselves into a child-sustained Sit Supported at 6 months. However, AD infants did not initiate this posture change until 12 months. Also, while HR and LR infants were first observed initiating a child-sustained Stand Supported at 9 months, AD infants were not observed initiating this posture until 14 months.  Furthermore, although the frequency of child-initiated posture changes increased in all groups from 6 to 12 months, AD infants initiated fewer posture changes overall than HR and LR infants combined (e.g., at 12 months, M_AD =14; M_LR/HR = 41.6).  At 14 months, however, this difference was no longer apparent.
Conclusions: These results suggest that in the first year of life, ASD infants exhibit delays in postural development.  Findings are discussed in terms of the potential cascading effects of such delays on opportunities for infant exploration and learning.