Research on Back Sleeping And SIDS

The single most effective action that parents and caregivers can take to lower a baby's risk of SIDS is to place the baby to sleep on his or her back for naps and at night.

Compared with back sleeping, stomach sleeping increases the risk of SIDS by 1.7 - 12.9.1 The mechanisms by which stomach sleeping might lead to SIDS are not entirely known. Studies suggest that stomach sleeping may increase SIDS risk through a variety of mechanisms, including:

  • Increasing the probability that the baby re-breathes his or her own exhaled breath, leading to carbon dioxide buildup and low oxygen levels
  • Causing upper airway obstruction
  • Interfering with body heat dissipation, leading to overheating2

Whatever the mechanism, evidence from numerous countries—including New Zealand, Sweden, and the United States—suggests that placing babies on their backs to sleep results in a substantial decline in the SIDS rate compared to placing babies on their stomachs to sleep. Researchers have established the link between stomach sleeping and SIDS by showing that babies who died from SIDS were more likely to be put to sleep on their stomachs compared to babies who lived. 

After that discovery, public health campaigns were launched to promote back sleep position and reduce the use of the stomach sleep position. Dramatic decreases in SIDS rates were observed in all countries with these public health campaigns; these campaigns have been successful in reducing the prevalence of stomach sleep position among infants. In areas where stomach sleeping is rare (including Hong Kong), SIDS rates historically have been very low, which further strengthens the association.3,4

Compared with infants who sleep on their backs, infants who sleep on their stomachs:

  • Are less reactive to noise
  • Experience sudden decreases in blood pressure and heart rate control
  • Experience less movement, higher arousal thresholds, and longer periods of deep sleep5,6

These characteristics might put an infant at higher risk of SIDS. The simple act of placing infants on their backs to sleep significantly lowers SIDS risk.

As stomach sleeping has declined in response to back-sleeping campaigns worldwide, statistics show that the contribution of side sleeping to SIDS risk has increased. Research shows that side sleeping is just as risky as stomach sleep position and, therefore, should not be used.7

Placing babies on their backs to sleep is not associated with risks for other problems. For example, there is no increase in aspiration or complaints of vomiting when babies are placed on their backs to sleep.8

Illustrations showing the back and stomach sleeping positions and the placement of the infant's trachea (tube to lungs) and esophagus (tube to stomach). Figure 1 shows the back sleep position in which the trachea lies on top of the esophagus. Figure 2 shows the stomach sleep position in which the esophagus in on top of the trachea.

Moreover, babies may benefit in other ways from sleeping on their backs. A 2003 study found that infants who slept on their backs were less likely than infants who slept on their stomachs to develop ear infections, stuffy noses, or fevers.9

Several studies found that back sleepers have delayed early motor skill milestones, although one recent Israeli study found no difference in gross motor developmental skills at 6 months among supine (back) and prone (stomach) sleepers.10,11Some studies have noted that even though supine sleepers experience these early delays, there is no significant age difference in terms of when the infants learn to walk.12,13

Multiple studies have found a positive correlation between the amount of time supine sleepers spend prone during their awake hours and motor skills development.14,15This finding reinforces the need to educate parents about the importance of tummy time.

  1. American Academy of Pediatrics, Task Force on Infant Sleep Position and Sudden Infant Death Syndrome. (2000). Changing concepts of sudden infant death syndrome: Implications for infant sleeping environment and sleep position. Pediatrics, 105(3), 650-656.
  2. Carroll, J. L., & Siska, E. S. (1998). SIDS: Counseling parents to reduce the risk. American Family Physician, 57, 1566-1567.
  3. Davies, D. P. (1985). Cot death in Hong Kong: A rare problem? Lancet, 2, 1346-1348.
  4. Lee, N. N., Chan, Y. F., Davies, D. P., Lau, E., & Yip, D. C. (1989). Sudden infant death syndrome in Hong Kong: Confirmation of low incidence. British Medical Journal, 298(6675), 721.
  5. Sahni, R., et al. (2002). Quality of diet, body position, and time after feeding influence behavioral states in low birth weight infants. Pediatric Research, 52, 399-404.
  6. Kahn, A., et al. (2003). Sudden infant deaths: Stress, arousal, and SIDS. Early Human Development, 75(Suppl.), 147-166.
  7. Li, D.k., Petitti, D.B., Willinger, M., et al. (2003). Infant sleeping position and the risk of sudden infant death syndrome in California, 1997-2000. American Journal of Epidemiology, 157(5): 446-455.
  8. American Academy of Pediatrics, Task Force on Infant Sleep Position and Sudden Infant Death Syndrome. (2000).
  9. Hunt, C. E., et al. (2003). Infant sleep position and associated outcomes. Archives of Pediatric and Adolescent Medicine, 157, 469-474.
  10. Majnemer, A., & Barr, R. G. (2005). Influence of supine sleep positioning on early motor milestone acquisition. Developmental Medicine & Child Neurology, 47, 370-376. 
  11. Carmeli, E., Marmur, R., Cohen, A., & Tirosh, E. (2009). Preferred sleep position and gross motor achievement in early infancy. European Journal of Pediatrics, 168, 711-715.
  12. Davis, B. E., Moon, R. Y., Sachs, H. C., & Ottolini, M. C. (1998). Effects of sleep position on infant motor development. Pediatrics, 102(5), 1135-1140.
  13. Pin, T., Eldridge, B., & Galea, M.P. (2007). A review of the effects of sleep position, play position, and equipment use on motor development in infants. Developmental Medicine & Child Neurology, 49, 858-867.
  14. Salls, J. S., Silverman, L. N., & Gatty, C. M. (2002). The relationship of infant sleep and play positioning to motor milestone achievement. American Journal of Occupational Therapy, 56(5), 577-580.
  15. Majnemer, A., & Barr, R. G. (2005).