A dramatic decrease of sudden infant death syndrome (SIDS) has been noted following the issuance of recommendations to adopt the supine sleeping position for infants. It has been suggested that the increased risk could be related to heat stress associated with body position. In the present study, the dry heat losses of small-for-gestational-age newborns nude or clothed were assessed and compared to see whether there is a difference in the ability to lose heat between the prone and supine positions. An anthropomorphic thermal mannequin was exposed to six environmental temperatures, ranging between 25 and 37°C, in a single-walled, air-heated incubator. The magnitudes of heat losses did not significantly differ between the two body positions for the nude (supine 103.46 ± 29.67 vs. prone 85.78 ± 34.91 W/m²) and clothed mannequin (supine 59.35 ± 21.51 vs. prone 63.17 ± 23.06 W/m²). With regard to dry heat exchanges recorded under steady-state conditions, the results show that there is no association between body position and body overheating.