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Cot death

Sudden infant death syndrome

The cause of cot death is not known. However, you can reduce the risk of cot death by the measures detailed below. The most important are to lay your baby on his or her back to sleep (not on their front or side) and to create a smoke-free zone for your baby.

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What is cot death?

Cot death is more properly known as sudden infant death syndrome (SIDS). It is the term used to describe the sudden death of a baby in its sleep where no cause or reason can be found.

How common is cot death?

Cot death is uncommon. About 1 in 4,166 babies die due to cot death each year in England and Wales, making a total of 150 unexplained deaths of infants aged under one year in 2020. This is lower than previous years, though it is possible that delays to death registrations due to the pandemic may have slightly influenced the figure. Most cases occur in babies under the age of 6 months.

The age range where there is the most risk is 2-4 months. However, the number of cases in the UK has fallen sharply since the introduction of the 'Back to sleep' campaign in 1991. (Before this twice as many babies died every year from cot death.)

This campaign was launched because research showed that the fashion at the time for placing babies to sleep on their front increased the risk of a cot death. The campaign has resulted in most parents now knowing that the safest position for a young baby to sleep is on their back.

In addition to the sleeping position, other factors can reduce the risk of a cot death. These are detailed below.

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What causes cot death?

We don't fully understand the cause and it is probably due to a combination of things. It is likely to affect babies who are more vulnerable for one reason or another. This could be, for example, because they were born too early (prematurely) or had a low birth weight. Environmental factors such as tobacco smoke, getting tangled in bedding or minor illness can cause stress to a baby and it is thought that those who die of cot death do not respond well to these types of stresses, perhaps being less well able to control their heart rate, breathing and temperature than other babies.

How to prevent cot death

Research has shown that the risk of cot death can be reduced. The things you can do fall into four main categories:

  • Sleeping - learn the best way for your baby to sleep.

  • Smoking - create a smoke-free home for your baby.

  • Symptoms of illness - see a doctor if your baby appears unwell.

  • Consider breastfeeding.


The best way for your baby to sleep is as follows. Make sure that any childminders or babysitters know this too.

Baby cot sleep position

Baby sleep position

Lay your baby on their back to sleep

In other words, do not lay him or her on their front or side. Cot death is less common in babies who sleep on their back. It is important to put babies on their backs for daytime naps and any other times of sleep, in addition to the longer night-time sleep.

The evidence shows that babies who sleep on their back are not more likely to choke than babies who sleep on their front. (This unfounded worry was why it was common to put babies on their front in the past.)

When your baby is aged about 5-6 months they will normally start to be able to roll over. At first, if you find that your baby has rolled over on to their front then turn them back on to their back.

However, you do not need to keep on checking in the night. Soon, they will be able to roll over and back again on their own and, like adults, they will toss and turn in their sleep. When they can do this it is fine for your baby to find their own position to sleep. The risk of cot death falls sharply at this age and it is safe for them to sleep in whatever position they like.


Do not use a pillow - just use a firm mattress that fits well into the cot, covered with a sheet. Use layers of sheets and thin blankets to cover your baby. Do not use duvets, quilts, or other soft, loose covers. Do this at least until the baby is 1 year old.

Duvets and loose covers are more likely to cover a baby's face. Also, using several thin layers allows you to put on or take off layers depending on the room temperature.

The newer baby 'sleeping bags' mean you do not have to use any additional bedding for your baby. The baby 'wears' the sleeping bag - a bit like a pinafore dress with the bottom sewn up. It is usually fastened with a zip and/or poppers. They come in different 'tog' weights, just like a normal duvet.

This means you can choose a sleeping bag of the appropriate warmth depending on whether it is summer or winter, or whether you live in a hot or a cold climate. Your baby can wear a vest, babygro or pyjamas, again depending on the warmth of the room in which they sleep.

The advantage of sleeping bags is that your baby cannot bury himself or herself under the covers. Sleeping bags also have the advantage that your baby cannot pull their covers off in the night and become too cold. Sleeping bags can also prevent a younger baby from rolling on to his or her front or side.

The sleeping bags are sized according to age and your baby must be a minimum weight to wear one - consult the manufacturers' labels for more information. This means they are usually not suitable for newborns - only for babies who are a few months old. Many parents now choose sleeping bags for their babies, although they can be quite expensive.

Do not place soft materials or objects such as pillows, quilts, comforters, or sheepskins under a sleeping baby. Also, keep stuffed toys and other soft objects out of the cot. If you use bumper pads in a cot they should be thin, firm, well secured and not 'pillow-like'. They should also be free from loose ties that present a strangle hazard.

Cover your baby up to their chest and shoulders only

The baby's head must be left uncovered. Tuck sheets and blankets under the sides of the mattress to stop them riding up on to the baby's face. Tuck them so they reach up to your baby's armpits but not above.

Some parents prefer not to use any sheets or blankets. They use 'sleeping bags' (detailed above) that are designed to keep the baby warm without the possible hazard of the head being covered in the night.

Lay your baby 'feet to foot'

That is, the baby's feet should be just touching the foot of the cot. This means they cannot slip further down the cot under the sheets or blankets.


Babies need to be warm but not too warm. Being too warm increases the risk of cot death. Have the room at a temperature that is comfortable for you. If your baby is sweating or feels hot then they are too warm. Do not place a baby's cot next to a heater or radiator, or in direct sunlight. Also, do not use hot water bottles, electric blankets, etc.

When you sleep, share a room with your baby - but not your bed

A cot or crib next to your bed is the best place for your baby to sleep until they are at least 6 months old.

It is best not to share a bed with your baby when you sleep (so-called 'co-sleeping'). There is a risk that you might roll over on to your baby when you are asleep, or your baby may become trapped under the bedclothes. It is normal to feed and cuddle your baby when you are resting in bed but awake. However, when it is time for you to sleep, the best place for your baby is in a cot next to your bed.

In particular, there is an increased risk when bed-sharing if:

  • Your baby was born prematurely, had a low birth weight (under 2.5kg), or is less than 3 months old.

  • You smoke - or your partner smokes - (even if you do not smoke in the home).

  • You are very tired or you are taking medication that can make you drowsy.

  • You have taken any alcohol or recreational drugs..

The baby should be placed in a Moses basket or a cot next to your bed. You can also get cots that attach to the side of your bed. The baby has his or her own area in which to sleep but there are no rails on the side next to you. This means you can feed your baby safely in bed (even breastfeeding lying down) but once finished, you can just slide the baby over into the cot.

Consider offering your baby a dummy when it is time to sleep

Some research studies have shown that the use of a dummy can reduce the risk of cot death, but not all experts agree on this. You could consider offering your baby a dummy at the start of each episode of sleep.

However, if you breastfeed, do not start to use a dummy until you are well established with breastfeeding. This is normally when the baby is about 1 month old. Also, it is common to stop using a dummy when the baby is about 6-12 months old, as prolonged use of a dummy may possibly lead to dental and/or speech problems.

However, do not force a dummy on a baby who does not want one. If the dummy falls out when a baby is asleep, just leave it out. Also, never coat a dummy with anything such as sweet liquids or sugar. Clean and replace dummies regularly.

Do not fall asleep with your baby on a sofa, armchair, settee, etc

This has been shown to increase the risk of cot death.


Create a smoke-free area around your baby. Cigarette smoke is a main 'risk factor' for cot death. Do not let anyone smoke in the same room as your baby. Smoking whilst pregnant also increases the risk of your baby having a cot death.

The greater the number of cigarettes smoked per day whilst pregnant, the greater the risk. If at all possible, do not smoke when you are pregnant. Your practice nurse, GP or midwife can give you advice and help if you want to stop smoking but are finding it difficult.

Symptoms of illness

Most cot deaths occur 'out of the blue' when the child is asleep. There are usually no symptoms to alert parents or carers that anything is wrong. However, sometimes an illness is not recognised and quickly becomes worse. See a doctor if your baby appears unwell. Use your instincts - you know best if something is not right.

The list below is also a guide to the main symptoms to look out for:

  • Being sick (vomiting), especially green (bile) vomit.

  • Taking less milk feed (fluids) and/or making less urine than usual.

  • High-pitched or unusual cry.

  • Drowsiness, floppiness or being less responsive than usual.

  • Wheezy, grunting, fast or difficult breathing.

  • High temperature (fever) or sweating a lot.

  • Looking pale or blue.

  • Blood in the nappies.

  • Rash.

Immunisation protects against serious illness. Babies who are fully immunised are less at risk of cot death. Immunisation does not cause autism. If you are concerned about something that you have read about immunisation, discuss it with your health visitor, practice nurse or GP. There is a lot of misinformation about immunisation on the internet and they should be able to reassure you that the benefits of immunisation vastly outweigh the risks and that you should immunise your baby.


Research studies have shown that breast-fed babies have a reduced risk of cot death compared to formula-fed babies. This may be partly explained by the fact that breastfed babies, on average, have fewer illnesses compared to formula-fed babies.

But there may be other factors. Breastfeeding also provides other advantages to both baby and mother. See the separate leaflet called Breastfeeding Your Baby for more information.

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Enjoy your baby

Cot death is uncommon and becomes rare after the age of 5 months - about the time when babies are able to roll over and move a bit more. Don't let the worry of cot death spoil the precious time of getting to know your baby.

However, the measures listed above reduce the small risk of cot death even further. The single most important thing is simply to remember to put your baby on his or her back when you place them down to sleep.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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