Cookies on the Bupa website

We use cookies to help us understand ease of use and relevance of content. This ensures that we can give you the best experience on our website. If you continue, we'll assume that you are happy to receive cookies for this purpose. Find out more about cookies


Cot death and sudden infant death syndrome (SIDS)

Key points

  • Less than half of all cot deaths have a specific cause.
  • Although it’s impossible to prevent SIDS, there are a number of things you can do to reduce the chances of it happening.
  • Ensuring your baby has a safe sleep environment and doesn’t overheat are just some of the things you can do to reduce the risk.

Cot death is when a baby under a year old dies suddenly and unexpectedly. If after a detailed investigation the death remains unexplained, the medical term is sudden infant death syndrome (SIDS). It's also known as sudden unexplained death in infancy (SUDI).

About cot death

More than 200 babies die suddenly and unexpectedly in the UK every year. Cot death can happen to any baby, but it's more common in babies between two to four months, premature babies, and babies with a low birth weight. It's also more common in baby boys than girls.

Most cot deaths happen when a baby is asleep in their cot at night.

What happens after a cot death?

If your baby was one of twins, triplets or more, you may need to take your other baby (or babies) into hospital for observation. This is important, as some rarer causes of sudden death in infancy run in families.

A thorough investigation will be done to try to find out why your baby died and to gather information that may help to prevent cot deaths in the future. This investigation is standard procedure in all cot deaths and doesn't in any way imply suspicion or blame surrounding your baby's death.

The people who will be involved in the investigation can vary depending on where you live. They may include a coroner (an official who enquires into sudden, unexpected deaths), a paediatrician (a doctor who specialises in children's health), a pathologist (a doctor who performs the autopsy), social workers, police officers, health visitors and midwives.

When the full results from the investigation are available, a case discussion meeting will take place, which will be attended by all of the people involved in the investigation. This may be up to 12 weeks after the death of your baby.

You will be kept informed of the investigation procedure and progress at all times. At the end of the investigation, a doctor will usually discuss the findings with you.

If a specific cause of death is found, this will be registered on the death certificate. If your baby’s death remains unexplained after the investigation, the death is usually registered as SIDS or SUDI.

Causes of cot death

Identified causes

Less than half of all cot deaths have a specific cause. Possible causes include a serious infection, an accident or a previously unknown problem that your baby was born with (a congenital condition). This may include a heart or lung problem. However, there are a large number of potential causes, which is the reason why the investigation has to be so thorough.


If no specific cause is found to explain the death of your baby, it's defined as SIDS or SUDI. Research suggests that a number of different factors may be linked to SIDS. These factors aren't thought to actually cause SIDS, but may make your baby more at risk. These factors can be divided into two groups – those that you can modify and those you can’t.

Factors you don't have any control over and can’t modify include:

  • the age of your child, as SIDS is more common in babies who are two to four months old
  • if your baby was born prematurely, particularly if you share a bed with your baby
  • having a family history of SIDS
  • the sex of your baby, as around seven out of 10 babies who die from SIDS are boys
  • your baby having a previous life-threatening event, such as if they stopped breathing

Risk factors you do have control over and can change or modify include:

  • your baby's exposure to cigarette smoke – both while you're pregnant and after your baby is born
  • placing your baby on their chest or side to sleep
  • using soft bedding, such as quilts, mattresses, pillows and duvets
  • using a second-hand mattress
  • sharing a bed with your baby or sleeping with your baby on the sofa
  • overheating – either from a high room temperature or from too much bedding

Reducing the risk of cot death

Although it’s impossible to prevent SIDS, there are a number of things you can do to reduce the chances of it happening.


  • If your baby is unwell, see your doctor promptly.
  • If your baby has a high temperature, try to keep him or her cool.


Exposure to cigarette smoke (during pregnancy or after birth) is known to increase the risk of cot death. One in five deaths from SIDS are thought to be linked to passive smoking.

  • Don't smoke during pregnancy – this applies to both mothers and fathers.
  • Don't let anyone smoke in the same room as your baby – ask them to smoke outside.
  • Don't share a bed with your baby if you or your partner smokes.


For the first six months, the safest place for your baby to sleep is in a cot or Moses basket in your bedroom.

  • Always lie your baby on his or her back to sleep.
  • Place your baby with their feet at the foot of the cot to prevent them wriggling down under the covers.
  • Don't fall asleep with your baby while you’re sitting or lying on a sofa or armchair.
  • Don't let your baby sleep with a pillow.
  • Use a firm mattress with a waterproof cover for your baby's cot.
  • Always make sure that bedding is tucked in securely.
  • Make sure your baby's head isn’t covered with bedding.

Don't share a bed with your baby if you or your partner:

  • have been drinking alcohol
  • have taken medication that makes you drowsy
  • are very tired
  • smoke


There is some evidence to suggest that giving your baby a dummy when you settle him or her to sleep may help to reduce the risk of cot death. However, more research is needed to understand why this is before official recommendations can be made regarding the risks and benefits of using dummies.

If you're breastfeeding, don't introduce a dummy until around a month (wait until your baby is breastfeeding well). Also, reduce the use of a dummy gradually when your baby is around six to 12 months to prevent dental problems.


Babies who are breastfed are less likely to die from cot death than babies who have only ever received formula milk.


Keep your baby at the right temperature.

  • The ideal room temperature for your baby is 18°C (a range of 16 to 20°C is acceptable).
  • Keep your baby's head uncovered.
  • Feel your baby's chest to check if he or she is the right temperature. If it's hot or your baby is sweating, take off some bedding or clothing. It's normal for babies to have cool hands and feet.
  • Always dress your baby in suitable clothing for the conditions – don’t add more than one layer of clothing than an adult would wear comfortably in the same environment.
  • Always take off your baby's outdoor clothes when you come inside, even if this means waking him or her up to do so.
  • Don't let your baby sleep with a hot water bottle or electric blanket, next to a radiator, heater or fire, or in direct sunshine.
  • Don't use duvets or quilts.
  • Baby sleeping bags are an alternative to blankets and sheets. Make sure you get the right size and thickness and know what clothes your baby should wear underneath. Always check the manufacturer's recommendations to ensure that your baby doesn't overheat.

Baby breathing monitors

There is no evidence that breathing or movement monitors help prevent cot death so only use one if your doctor advises you to.

Living with cot death

Even after you take as many precautions as possible, babies can and do still die from cot death. You may have many different emotions and some parents have overwhelming feelings of guilt and anger. Family and friends can be a valuable source of help and comfort at this difficult time. They can also help in practical ways, for example if you have other children, they can look after them for you, prepare meals and do the shopping.

Dedicated charities, support groups and associations offer advice and help to families affected by cot death. It may also help to talk to a counsellor who specialises in helping people cope with grief. Your GP or health visitor can help you find a suitable counsellor or support group in your area.

Having another child

The decision to have another child after losing a baby to cot death isn't an easy one. You will know if and when you're ready and when it’s the right time for you.

Care of the next infant (CONI) schemes are available in many areas. They offer advice, support, increased monitoring for your new baby and frequent check-up visits. Ask your GP or midwife if there is a CONI scheme in your area. If there isn't, your local health authority may run its own equivalent scheme. They may be able to offer you additional support during your pregnancy and after the birth of your new child.


Reviewed by Rachael Mayfield-Blake, Bupa Heath Information Team, August 2013.

Find out more about our health editors


For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.

Share with others

  • This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.

    Approved by Plain English Campaign The Information Standard memberHON Code