Occupational therapists working with infants in neonatal intensive care units (NICUs) make positioning recommendations to optimize self-regulation, with little published data supporting this practice. In this retrospective descriptive study, 15 hospitalized preterm infants (M_{gestational age} = 32 weeks) were videotaped during noncaregiving periods in order to record the frequency of specific behaviors in relation to six infant positions (prone nested, prone un-nested, side-lying nested, side-lying un-nested, supine nested, and supine un-nested). Behaviors coded were those that suggest infant stress or motor efforts at self-regulation, as defined for the original study. Mixed effects regressions and post-hoc Tukey Honestly Significant Difference tests were used to analyze the data, after the calculation of a ratio of the number of behaviors in each position. Higher ratio values reflect a greater occurrence of behaviors.

The number of motor self-regulatory and stress behaviors were related to infant position, with the highest ratios of behaviors observed in side-lying un-nested and the lowest in prone nested. Behavior ratios did not differ between prone un-nested and prone nested, nor between supine un-nested and supine nested. More self-regulatory and stress behaviors were related to longer periods of fussing and crying. Longer periods of light sleep were related to fewer stress behaviors.

Infants performed the fewest stress behaviors in prone nested, prone un-nested, or side-lying nested. These positions may benefit infants in the NICU by reducing the need for motor-based self-regulatory behaviors and potentially conserving energy for growth.