SIDS – Sudden Infant Death Syndrome

Sudden infant death syndrome (SIDS) – also known as cot death – is the sudden, unexpected and unexplained death of an apparently well baby. In the UK, at least 300 babies die suddenly and unexpectedly every year. Most unexpected deaths occur during the first six months of a baby’s life while the child is asleep in their cot at night. (1)

Despite declines in prevalence during the past two decades, sudden infant death syndrome (SIDS) continues to be the leading cause of death for infants aged between 1 month and 1 year in developed countries. (2)

What causes SIDS?

No-one knows exactly what causes SIDS, but it is thought to be the result of a combination of factors. Experts believe SIDS occurs at a particular stage in a baby’s development, and that it affects babies who are vulnerable to certain environmental stresses. This vulnerability may be due to being born prematurely or to low birthweight, or other reasons not yet identified. Current medical and scientific evidence explains SIDS as a multifactorial disorder arising from a combination of genetic, metabolic, and environmental factors (3)

Infant risk factors

Large-scale epidemiological studies over the last two decades have increased our understanding of SIDS and identified certain modifiable risk factors – that is risk factors parents can take action to prevent. The most important modifiable risk factors for SIDS are infants sleeping in the prone position (face down) and maternal smoking during pregnancy (1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12,13 &14). Risk factors identified in these studies include:

  • Prone (face down) and side sleeping positions
  • Tobacco smoke exposure
  • Soft bedding and sleep surfaces
  • Face covered by bedding
  • Overheating/Thermal stress
  • Infants born prematurely or with a low birth weight
  • Sex - SIDS is more common in baby boys
  • Age (peak 2-4 months)
  • Sharing a bed with parents or siblings
  • Sleeping in own room rather than in parents’ room

An article in The American Academy of Pediatrics divides risk factors into two categories (15):

  • Male gender
  • Prematurity
  • Genetic polymorphisms
  • Prenatal exposure to cigarettes and/or alcohol
  • Prone or side sleep position
  • Bed sharing
  • Overbundling
  • Soft bedding
  • Face covered

The authors studied SIDS cases in San Diego County after the initiation of the Back To Sleep campaign. They note that most SIDS infants were subject to at least 1 intrinsic risk factor and at least 2 extrinsic risks. They advocate risk reduction campaigns emphasising the importance of multiple and simultaneous SIDS risks as essential in preventing SIDS: that is reducing as many risk factors as possible.

Babies who die of SIDS are thought to have problems in the way they respond to these stresses and how they regulate their heart rate, breathing and temperature. Although the cause of SIDS is not fully understood, there are things you can do to reduce the risk (see below).

What can I do to help prevent SIDS?

Follow the advice below to helps prevent SIDS:

  • Always place your baby on their back to sleep (even for naps)
  • Don't smoke during pregnancy or let anyone smoke in the same room as your baby
  • Let your baby sleep in the same room (NOT the same bed) as parents, in their own cot
  • Keep your baby’s head uncovered
  • Don't use duvets, quilts, baby nests, wedges, bedding rolls or pillows
  • Sleep positioners or any other infant sleep positioning devices should NOT be used as they pose a risk of suffocation
  • Don't share a bed with your baby
  • Never sleep with your baby on a sofa or armchair.
  • Don't let your baby get too hot or too cold. The room temperature should be confortable for a lightly clothed adult
  • Place your baby in the "feet to foot" position (with their feet touching the end of the cot or pram).
  • If possible, breastfeed your baby

Read more about reducing the risk of cot death

How does LifeNest help prevent SIDS?

  • LifeNest encourages the back-sleeping position without the use of bolsters or other positioning devices that pose a suffocation risk
  • LifeNest reduces suffocation risk as the mesh hammock is fully breathable, even if your baby rolls over onto their stomach
  • LifeNest promotes natural air circulation to disperse excess heat and help prevent overheating
  • LifeNest reduces the risk of re-breathing CO2 as the mesh hammock and venting channels quickly eliminate the CO2 a baby breathes out for better oxygenation
  • LifeNest allows liquids and secretions pass right through the netting to help avoid any potentially dangerous airflow blockages

The LifeNest sleeping system is designed help eliminate many of the environmental risk factors that have been linked to SIDS through large-scale epidemiological studies. As most SIDS cases appear to be multifactorial (15), we believe in eliminating as many of the known risks as possible.


  2. Moon, Rachel Y., Rosemary SC Horne, and Fern R. Hauck. "Sudden infant death syndrome." The Lancet 370.9598 (2007): 1578-1587
  3. Willinger, M., James, L.S., & Catz, C. (1991). Defining the sudden infant death syndrome (SIDS): Deliberations of an expert panel convened by the National Institute of Child Health and Human Development. Fetal and Pediatric Pathology, 11, 5, 677-684.
  4. Canadian Medical Association CMAJ June 20, 2006 vol. 174 no. 13 doi: 10.1503/cmaj.051671
  5. Mitchell, E.A., Taylor, B.J., Ford, R.P.K., Stewart. A.W., Becroft, D.M.O., Thompson, J.M.D., Scragg, R., Hassall, I.B., Barry, D.M.J., Allen, E.M., Roberts, A.P. (1992). Four modifiable and other major risk factors for cot death: The New Zealand Study. Journal of Paediatric Child Health, 28, Supplement 1, S3-8.
  6. Blair, P.S., Fleming, P.J., Bensley, D., Smith, I., Bacon, C., Taylor, E., Berry, J., Golding, J., & Tripp, J. (1996). Smoking and the sudden infant death syndrome: Results from 1993-1995 case-control study for confidential inquiry into stillbirths and deaths in infancy. British Medical Journal, 313, 195-198.
  7. Oyen N., Markestad, T., Skjaerven, R., Irgens, L., Helweg-Larsen, K., Alm, B., Norvenius, G., & Wennergren, G. (1997). Combined effects of sleeping position and prenatal risk factors in sudden infant death syndrome: The Nordic Epidemiological SIDS study. Pediatrics, 100, 613-621.
  8. Brooke, H., Gibson, A., Tappin, D., & Brown, H. (1997). Case-control study of sudden infant death syndrome in Scotland, 1992-5. British Medical Journal, 314, 1516-1520.
  9. Alm, B., Milerad, J., Wennergren, G., Skjaerven, R., Oyen, N., Norvenius, G., Daltveit, A-K., Helweg-Larsen, K. Markestad, T., Irgens, L.M. and the Nordic Epidemiological SIDS Study. (1998). A case-control study of smoking and sudden infant death syndrome in the Scandinavian countries, 1992-1995. Archives of Diseases in Children, 78, 329-334.
  10. Carpenter, R.G., Irgens, L.M., Blair, P.S., England, P.D., Fleming, P., Huber, J., Jorch, G., & Schreuder, P. (2004). Sudden unexplained infant death in 20 regions in Europe: Case-control study. Lancet, 363, 185-91.
  11. Gessner, B.D., Ives, G.C., Perham-Hester, K.A. (2001). Association between sudden infant death syndrome and prone sleep position, bed sharing, and sleeping outside an infant crib in Alaska. Pediatrics. 108, 923-927.
  12. Vennemann, M., Findeisen, M., Butterfab-Bahloul, T., Jorch, G., Brinkman, B., Kopcke, W., Bajanowski, T., Mitchell, E., & the GeSID Group. (2005). Modifiable risk factors for SIDS in Germany: Results of GeSID. Acta Paediatrica, 94, 655-660.
  13. Hauck, F.R., Herman, S.M., Donovan, M., Iyasu, S., Moore, C.M., Donoghue, E., Kirshner, R.H., & Willinger, M. (2003). Sleep environment and the risk of sudden infant death syndrome in an urban population: The Chicago infant mortality study. Pediatrics, 111, 1207-1214.
  14. Fleming, P., & Blair, P. (2007). Sudden infant death syndrome and parental smoking. Early Human Development, 83, 11, 721-725.
  15. Trachtenberg, Felicia L., et al. "Risk factor changes for sudden infant death syndrome after initiation of Back-to-Sleep campaign." Pediatrics 129.4 (2012): 630-638.