Introduction

Sudden infant death syndrome (SIDS) is a condition in which a baby dies suddenly while sleeping, and doctors can't find a cause. It's also called cot death. Sudden infant death syndrome isn't common, and it's rare in babies more than 6 months old. But there are some simple things you can do make it even less likely.

We've brought together the best research about cot death and weighed up the evidence about how to reduce the risk. You can use our information to talk to your doctor, nurse, or health visitor, and decide the best way of putting your baby to bed.

Sudden infant death syndrome (SIDS or cot death) occurs when a baby under 12 months old dies suddenly for no apparent reason. When doctors do an investigation into the death (a post mortem), they can't find anything that might have been the cause.

Sudden infant death syndrome (also known as cot death) happens without any warning when a baby is thought to be sleeping. It can occur when a baby is in a cot, but babies can also die when they're sleeping somewhere else, such as in a pram or their parent's arms.^[1]

Babies who die of cot death usually die peacefully in their sleep. They show no signs of pain or distress.^[1] There aren't any symptoms or warning signs.

Doctors don't know what causes cot death. It's more common in the first four months of a baby's life.^[2]

Research has found several things that seem to be linked to babies dying unexpectedly. These are known as risk factors.^[3][4]

• Babies seem to be more at risk if they are placed to sleep on their front. This is the most important factor. It's safer to place your baby to sleep on their back.

• There's also a higher risk of SIDS if the baby's mother or another family member smokes.

Risk factors make cot death more likely. But it's important to realise that having a risk factor doesn't mean cot death will happen. We know only that babies who die of cot death are more likely to have been exposed to these risks.

Avoiding these risk factors can help make cot death less likely. To read more about things you can do, see What helps to reduce the risk of sudden infant death syndrome?

Do I need a monitor?

Some companies sell devices that monitor a baby's breathing. Doctors sometimes suggest using these for babies who have a medical condition that affects their breathing. And they're sometimes given to parents who've lost a baby to cot death and go on to have another child. But there's no evidence that home breathing monitors can reduce the risk of cot death.^[5] Doctors don't usually recommend using them.