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Sudden infant death syndrome (SIDS)

5-minute read

Sudden Unexpected Death in Infancy (SUDI) is a term used to describe the sudden and unexpected death of a baby. SUDI may be the result of a serious illness or a problem that baby may have been born with, but most SUDI deaths occur as a result of either SIDS or a fatal sleep accident.

When no cause for the death can be found, it is called ‘SIDS’. Sudden infant death syndrome (SIDS), is the sudden, unexpected and unexplained death of an apparently well baby. In Australia in 2016, 94 babies died suddenly and unexpectedly; of these deaths, 54 were identified as SIDS.

SUDI is rare and the risk of your baby dying from it is very low.

Most deaths happen during the first 3 months of a baby’s life. Infants born prematurely or with a low birth weight are at greater risk, and SIDS is also more common in baby boys. Most unexpected deaths occur while the child is asleep in their cot at night.

However, SIDS can also occur when a baby is asleep during the day or, occasionally, while they are awake. Mothers can reduce the risk of SIDS by not smoking while pregnant or after the baby is born, and always placing the baby on their back when they sleep.

What causes SUDI, including SIDS and fatal sleep accidents?

Sudden and unexpected deaths in babies as a result of a medical problem are probably not preventable. However, scientists have identified similar risk factors that are present in SIDS, SUDI and fatal sleep accidents. By removing known risk factors and providing a safe sleeping environment most of these deaths are preventable.

No one knows exactly what causes SUDI, 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 birth weight, or other reasons not yet identified. Environmental stresses could include tobacco smoke, getting tangled in bedding, minor illness or having a breathing obstruction.

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, you can reduce the risk.

What can I do to help reduce the risk of SUDI, including SIDS and fatal sleep accidents?

Follow the advice below to help prevent SUDI:

  • sleep baby on their back
  • keep head and face uncovered
  • keep baby smoke free before and after birth
  • safe sleeping environment night and day
  • sleep baby in a safe cot in parents' room
  • breastfeed baby

A safe sleep environment

  • Place your child on their back to sleep. The safest place for them to sleep is in a cot in a room with you for the first 6 to 12 months.
  • Do not smoke while you are pregnant or after your baby is born, and do not let anyone else smoke in the same room as your baby.
  • Sharing a sleeping surface with a baby increases the risk of SUDI in some circumstances. Babies who are most at risk are those less than four months old, premature babies and those who are small for gestational age (low birth weight).
  • Avoid falling asleep with your baby on a sofa or an armchair.
  • Do not let your baby get too hot.
  • Keep your baby’s head uncovered. Their blanket should be tucked in no higher than their shoulders.

Place your baby on their back to sleep

Place your baby on their back to sleep from the very beginning, for both day and night sleeps. This will reduce the risk of SUDI. It’s not as safe for babies to sleep on their sides as on their backs. Healthy babies placed on their backs are not more likely to choke.

When the baby is old enough to roll over, don’t prevent them from doing so.


Exposure to cigarette smoke can significantly increase your baby’s risk of dying suddenly and unexpectedly. This applies to mothers who smoke during pregnancy and after the birth and also to those smoking around the baby.

If you smoke during pregnancy, your baby is much more likely to die from SUDI than if you don’t.

If your baby is exposed to a smoky environment after they are born, they are much more likely to die from SUDI compared to an infant living in a smoke-free environment. If you smoke, your doctor can recommend appropriate treatment and local support services to help you quit.

Don’t let anyone smoke in the same room as your baby

Babies exposed to cigarette smoke after birth are at increased risk of sudden and unexplained death. Nobody should smoke in the house, including visitors.

Anyone who needs to smoke should go outside. Don’t take your baby into smoky places.

Checklist for safe sleeping

Red Nose has compiled the following checklist for safe sleeping:

  • Has baby been placed on his or her back to sleep?
  • Is baby sleeping in a safe bassinette or cot, and away from hazards?
  • Does the cot meet the Australian Standard for cots?
  • Is the mattress firm?
  • Does the mattress fit the cot or bassinette well?
  • Is the mattress clean and in good condition and flat (not tilted or elevated)?
  • Is baby’s face and head uncovered?
  • Have any pillows, duvets, lambs wool, cot bumpers and soft toys been removed?
  • If using a baby sleeping bag, does it have a fitted neck, armholes or sleeves and no hood?
  • If using blankets rather than a sleeping bag, has baby been placed to sleep with feet touching the bottom of the cot/bassinette with blankets securely tucked in?
  • Is baby having tummy time to play when awake and supervised?
  • If you are a smoker have you stopped smoking or contacted your doctor or Quitline for help?
  • Remember never to sleep baby on a sofa, bean bag, waterbed or pillow.
  • Are other family members aware of how to sleep baby safely?

Read more about safe sleep for your baby.

For more information on SIDS and safe sleeping, please visit Red Nose at

Minimising the risk of SIDS - video

Video provided by Raising Children Network.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: June 2018

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