As a result of the American Academy of Pediatrics' recommendation that healthy infants be placed on their side or back for sleep, the percentage of infants sleeping prone has decreased dramatically. With the increase in supine sleeping, pediatricians have questioned if there are differences in the rate of acquisition of early motor milestones between prone and supine sleeping infants.


To examine this question, we performed a prospective, practice-based study of healthy term infants. Infants were recruited before the age of 2 months. Parents were asked to record infant sleep position and awake time spent prone until 6 months of age. A developmental log was used to track milestones from birth until the infant was walking. Age of acquisition of eight motor milestones was determined, and the mean ages of milestone attainment of prone and supine sleepers were compared.


Three hundred fifty-one infants completed the study. Prone sleepers acquired motor milestones at an earlier age than supine sleepers. There was a significant difference in the age of attainment of rolling prone to supine, tripod sitting, creeping, crawling, and pulling to stand. There was no significant difference in age when infants walked.


The pattern of early motor development is affected by sleep position. Prone sleepers attain several motor milestones earlier than supine sleepers. However, all infants achieved all milestones within the accepted normal age range. Pediatricians can use this information to reassure parents. This difference in milestone attainment is not a reason to abandon the American Academy of Pediatrics' sleep position recommendations.

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