Purpose: The purpose of this study was to describe the gross motor development of infants who slept supine and spent different amounts of time in the prone position when awake.
Method: Thirty infants who were six months old and slept supine were evaluated using the Alberta Infant Motor Scale (AIMS) and then divided into two groups: prone (n = 16) and no prone (n = 14) based on the number of times per day they were placed in prone position while awake.
Results: The prone group scored higher than the no prone group on the AIMS total scores (U = 36, p = 0.004), total percentile scores (U = 42, p = 0.003), and prone subscale scores (U = 25, p < 0.001).
Conclusions: Gross motor performance as measured by the AIMS was more advanced in infants who slept supine and had been placed in the prone position when awake than in infants who slept supine but had limited or no experience in the prone position while awake. The influence of awake positioning needs to be considered when interpreting the developmental motor performance of infants who are six months old.