The recordings of 1197 overnight rectal temperatures from infants of u
p to 24 weeks of age have been analysed with respect to 12 variables,
including a number of risk factors for sudden infant death syndrome. M
ultivariable regression was used to identify if parental smoking, bott
le feeding, sleeping position, and birth weight affect the overnight r
ectal temperature of infants. The rectal temperature, averaged over th
e period from three to five hours after the infants were put to bed, c
orrelated well (R=0.36) with the collected variables. An increase in t
he infant's age, birth weight, and the supine sleeping position all de
creased the night time rectal temperatures. However, an increase in th
e night time room temperature, weight, and the combination of bottle f
eeding and parental smoking produced an increase in rectal temperature
. The individual effects of bottle feeding and parental smoking were n
ot significant. The results show that some of the major risk factors h
ave the effect of raising the rectal temperature of sleeping infants.