 In 1987 the Netherlands started a campaign advising parents to place their newborn infants to sleep on their backs (supine position) instead of their stomachs (prone position).This was followed by infant supine sleep position campaigns in the United Kingdom (as "Back to Sleep"), New Zealand, and Australia in 1991, the U.S. and Sweden in 1992, and Canada in 1993.This advice was based on the epidemiology of SIDS and physiological evidence which shows that infants who sleep on their back have lower arousal thresholds and less slow-wave sleep (SWS) compared to infants who sleep on their stomachs.