this was an unblinded study that may have allowed introduction of reporting bias related to those variables that relied on perception (nurses' perception of infant sleep-restfulness, nurses' assessment of infant pain, parents'perceptions of infant comfort/crying). Parental ratings were not completed on 22 of the babies enrolled in the study.Given the exploratory nature of this study, extraneous variables including infant positioning, environmental lighting and noise levels, and the frequency and timing of painful procedure were not controlled and could have affected the results. A concurrent practice change lowered the mean chronologic age at study entry in the babies enrolled in the intervention group to 0.55 days compared to 1.18 days for the control group. This variance had little bearing on adjusted chronologic ages during the study period but may have had an impact on the results related to weight loss.