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Sudden infant death syndrome (SIDS)

Sudden infant death syndrome (SIDS) is the sudden and unexplained death of an apparently healthy baby aged up to 12 months old. It used to be called cot death.

What causes sudden infant death syndrome (SIDS)?

Sudden infant death syndrome (SIDS) is rare, but it does still happen.

It's not known what causes SIDS. But certain things can increase the risk of SIDS, like exposing a baby to cigarette smoke or sleeping with them on a sofa or chair.

Babies born early (before 37 weeks) or with a low birth weight (less than 2.5kg or 5.5lb) are more at risk of SIDS. So twins and multiples are more at risk of SIDS.

SIDS is more likely to happen in the first 6 months of life, but it can affect babies up to 12 months old. SIDS can happen anytime a baby is asleep, day or night.

How to reduce the risk of sudden infant death syndrome (SIDS)

There are things you can do to lower the risk of sudden infant death syndrome (SIDS). Follow this advice whenever your baby is sleeping.

If your baby was born prematurely, follow the advice for safer sleep for a year from their due date not the date they were born.

Do

  • always place your baby on their back to sleep in the feet-to-foot position – this means with their feet at the bottom of the cot, Moses basket or pram

  • move your baby onto their back if they roll (until they can roll onto their front and back again by themselves)

  • place your baby in a separate cot or Moses basket in the same room as you for every sleep for at least the first 6 months

  • use a firm, flat mattress

  • keep your baby's cot clear of anything that could cover their face and head – do not use pillows, duvets, cot bumpers, loose blankets, soft toys or anything to keep your baby in place, like pods or nests

  • breastfeed your baby if you can – breastmilk protects your baby from infections and diseases

  • think about using a dummy to settle your baby to sleep – some research suggests this can help lower the risk of SIDS

  • make sure your baby is up to date with their routine NHS vaccinations – these provide protection against childhood illnesses that may increase the risk of SIDS

Don't

  • do not sleep on a sofa or in an armchair with your baby

  • do not smoke when you're pregnant or around your baby after they're born, and do not let anyone smoke in the same room as your baby

  • do not share a bed with your baby if they were born prematurely (before 37 weeks of pregnancy) or if they weighed less than 2.5kg or 5.5lb when they were born

  • do not share a bed with your baby if you or your partner smoke, drink alcohol or take drugs or medicine that makes you feel sleepy (drowsy)

  • do not let your baby get too hot or too cold – make sure that your baby's room is between 16C to 20C

  • do not let your baby stay in a car seat for too long – it's ok for your baby to fall asleep in a car seat while you are travelling, but take your baby out of the car seat as soon as you get to where you're going

Information:

Find out more

How to make sure your baby doesn't get too hot or cold

Overheating can increase the risk of SIDS. Babies can overheat because of too much bedding or clothing, or because the room is too hot.

Check your baby's temperature by feeling their chest or the back of their neck. Do not worry if their hands or feet feel cool, this is normal.

To reduce the risk of SIDS:

  • keep the room at a temperature between about 16 to 20C – monitor the temperature using a room thermometer
  • remove 1 or more layers of clothing or bedding if your baby skin is hot or sweating
  • use lightweight blankets, sheets or a baby sleeping bag
  • remove hats and extra clothing as soon as you come indoors or enter a car, bus or train even if it means waking your baby

Babies should never sleep with a hot water bottle or electric blanket, next to a radiator, heater or fire, or in direct sunlight.

Information:

Find out more

How to be safe if you share a bed with your baby

The safest place for your baby to sleep is in a separate cot or Moses basket that is free from toys, blankets and pillows, as this reduces the risk of sudden infant death syndrome (SIDS).

If you do share a bed with your baby (co-sleeping) at any time, it's important to know how to do it safely and when to avoid co-sleeping with your baby.

Co-sleeping more safely

If you share a bed with your baby you should:

  • make sure they sleep on a firm, flat mattress lying on their back
  • keep pillows, sheets and blankets away from your baby
  • not swaddle your baby (baby sleeping bags are safer)
  • not have other babies, children or pets in the bed at the same time
  • not leave them alone in an adult bed (if there is not an adult in bed with them, put them in a crib, cot or Moses basket)
  • make sure your baby cannot fall out of bed, or become trapped between the mattress and wall

When co-sleeping is not safe

Do not share a bed with your baby if they were born premature (before 37 weeks of pregnancy) or if they had a low birthweight (less than 2.5kg or 5.5lb).

You should also not share a bed with your baby if you or your partner:

  • smoke (no matter where or when you smoke and even if you never smoke in bed)
  • have had 2 or more units of alcohol
  • have taken recreational drugs
  • have taken medicine that makes you feel sleepy (drowsy)
Information:

Find out more

How to use a baby sling or carrier safely

If you use a sling or baby carrier, make sure you use it safely to reduce the risk of SIDS.

It's not safe to feed your baby while they are in a sling. If you need to feed your baby, take them out of the sling.

When using a sling or carrier do not let the material cover your baby's head.

It's recommended to follow the T.I.C.K.S. rules for safe babywearing:

  • Tight – slings and carriers should be kept tight enough to hug your baby close to your body
  • In view – you should be able to see your baby's face at all times
  • Close – the sling should keep your baby close enough to kiss their head
  • Keep – keep your baby's chin off their chest
  • Support – support your baby's back so it is comfortably upright
Information:

Find out more

Urgent advice: Get an urgent GP appointment or contact 111 if:

  • you're worried about your baby or think they might be ill

Immediate action required: Call 999 if:

  • your baby stops breathing
  • will not wake up
  • your baby is struggling for breath
  • your child is stiff, shaking or jerking (this may be a seizure or fit)
  • your child's lips, tongue, face or skin suddenly turn pale, blue or grey (on black or brown skin this may be easier to see on the palms of the hands or the soles of the feet)
  • your child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
Information:

Do not drive yourself to A&E.

The person you speak to at 999 will give you advice about what to do.

Help and support for sudden infant death syndrome (SIDS)

The Lullaby Trust

The Lullaby Trust has information and advice on safer sleep for parents.

They also provide advice and support for families affected by SIDS.

Page last reviewed: 25 November 2025
Next review due: 25 November 2028