The Safe to Sleep campaign, formerly known as the Back to Sleep campaign, is an initiative backed by the US National Institute of Child Health and Human Development (NICHD) at the US National Institutes of Health to encourage parents to have their infants sleep on their backs (supine position) to reduce the risk of sudden infant death syndrome, or SIDS. The target age group of the campaign is 0–1 years of age, because this is when babies are at the greatest risk of experiencing SIDS. Since "Safe to Sleep" was launched in 1994, the incidence of SIDS has declined by more than 50%. However, there has been a rise in infant sleep-related suffocation events. Consequently, the campaign has broadened its goal to focus on safe sleep conditions and further preventative measures.

The campaign was successful in significantly reducing the percentage of babies sleeping on their stomachs (prone position). It was found, however, that a significant portion of African-American babies were still sleeping on their stomachs; in 1999, an African-American baby was 2.2 times more likely to die of SIDS than a white baby. Thus, then Secretary of Health and Human Services Donna Shalala and Tipper Gore refocused the "Back to Sleep" campaign on minority babies.

In 1992, the American Academy of Pediatrics (AAP) recommended that babies sleep on their backs or sides to reduce the risk of SIDS (a revised statement in 1996 retracted the side-sleeping option). NICHD launched the "Back to Sleep" campaign in 1994 to spread the message.

The campaign was successful in significantly reducing the percentage of babies sleeping on their stomachs (prone position). It was found, however, that a significant portion of African-American babies were still sleeping on their stomachs; in 1999, an African-American baby was 2.2 times more likely to die of SIDS than a white baby. Thus, then Secretary of Health and Human Services Donna Shalala and Tipper Gore refocused the "Back to Sleep" campaign on minority babies.

In 1985 Davies reported that in Hong Kong, where the common Chinese habit was for supine infant sleep position (face up), SIDS was a rare problem. 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 showed 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. Thus, these infants are more easily awakened. However, the arousal thresholds have been shown to be higher during SWS causing infants to be less easily awakened.

In human infants, sleep develops rapidly during early development. This development includes an increase in non-rapid eye movement (NREM) sleep – which is also called quiet sleep (QS) – during the first 12 months of life, in association with a decrease in rapid eye movement (REM) sleep – which is also known as active sleep (AS). In addition, slow wave sleep (SWS) – which consists of stage 3 and stage 4 NREM sleep – appears at 2 months of age, and it is theorized that some infants have a brain-stem defect which increases their risk of being unable to arouse from SWS (also called deep sleep) and therefore have an increased risk of SIDS due to their decreased ability to arouse from SWS.

Studies have shown that preterm infants, full-term infants, and older infants have greater time periods of quiet sleep and also decreased time awake when they are positioned to sleep on their stomachs, meaning these babies are harder to wake when sleeping on their tummy. In both human infants and rats, arousal thresholds have been shown to be at higher levels in the electroencephalography (EEG) during slow-wave sleep.