Night time rectal temperature recordings were made from 103 infants sl
eeping in their own home in different sleeping positions, In most case
s sleeping position was verified by video monitoring throughout the ni
ght. In the period before an adult-like night time body temperature pa
ttern appeared there was no significant effect of sleeping position up
on night time body temperature, in line with previous reports. Once an
adult-like night time temperature pattern appeared, infants sleeping
supine reached significantly lower rectal temperatures than those slee
ping prone or lateral. Babies sleeping supine moved significantly more
during the night and were more likely to uncover their hands and arms
. These findings suggest that supine sleepers are in a different physi
ological condition from those sleeping prone or lateral, which may be
associated with their lower vulnerability to sudden unexpected infant
death.