To evaluate effects of prone (P) versus supine (S) sleeping position in healthy preterm infants, 20 infants [mean birth weight 1661 ± 435g and mean gestational age 31 ± 2 wks] in the Intermediate Care Nursery at Packard Children's Hospital at Stanford between August 1994 and July 1995 were randomized at 33 weeks post-conceptional age (PCA) to either P (n=13) or S(n=7) sleeping position until discharge. Clinical data regarding weight, apnea, bradycardia [heart rate (HR) < 100], desaturations (oxygen saturation < 95%), and feeding were collected from the nursing records.

Birth weight and gestational age were similar for the two groups. The clinical outcome, as measured by PCA and weight at discharge (D/C), was not influenced by the sleeping position: PCA at D/C: 35.4 ± 0.8 wks (P) vs. 35.0 ± 0.6 wks (S); weight at D/C: 2182 ± 274g (P) vs. 2172± 159g (S). The PCA at full nipple feeds was not significantly different: 34.5 ± 0.8 wks (P) vs. 34.1 ± 0.4 wks (S). The overall incidence of apnea, bradycardia, and desaturations per infant did not differ based on sleeping position. However, at specific post-conceptional ages, differences were noted. In the first 30 minutes following feeds, supine infants had more apnea at 34 wks PCA (p<.002), more bradycardia at 34 and 35 wks PCA (p<.01), and more desaturations at 34 wks PCA (p<.001). In contrast, during nonfeeding times supine infants had less apnea at 34 wks PCA(p=.02). Based on severity of episodes, supine infants had more mild desaturations (90-94%) at 35 wks (p<.001) and more mild apnea (defined as no significant decrease in HR or saturation) at 33 wks PCA (p=.03) but less moderate bradycardia (HR 61-79) at 33 wks PCA (p=.03). Some changes in clinical care were noted, notably elevating the head of the crib (3S, 5P) or placing the infant in a side-lying position for thirty minutes after feeds(5S), but diagnostic testing for gastroesophageal reflux was not undertaken.

Supine sleeping position was associated with more labile respiratory status following feeds at 34 and 35 wks PCA, as measured by clinical monitoring of apnea, bradycardia, and desaturations. This difference was not evident at 33 wks nor at 36 wks PCA. The changes in clinical respiratory variables seen with supine positioning could reflect mild gastroesophageal reflux, although there was no adverse effect on weight and PCA at discharge. Use of supine positioning in monitored preterm infants prior to discharge may help to identify those who will not tolerate this position. Future studies to document effects of sleeping position on healthy preterm infants should include polysomnography with esophageal pH monitoring for reflux.