What is sudden infant death syndrome (SIDS)?

Sometimes a baby who seems healthy dies during sleep. This is called sudden infant death syndrome or SIDS. SIDS is also known as crib death.

In most cases, a parent or caregiver places the baby down to sleep and returns later to find the baby has died. It’s no one’s fault. SIDS can happen even when you do everything right.

Although SIDS is rare, it is one of the most common causes of death in babies between 1 and 12 months of age. Most babies who die of SIDS are between the ages of 2 and 4 months. More boys than girls die of SIDS, and most deaths occur in the winter.¹

What causes SIDS?

Doctors don't know what causes SIDS. It seems to happen more often in premature and low-birth-weight babies. It also is seen more often in babies whose mothers did not get medical care during the pregnancy and in babies whose mothers smoke. SIDS may also be more likely in babies who were part of a multiple pregnancy (for example, twins or triplets) or whose mothers are younger than 20.

When babies sleep on their bellies, they may not breathe well. Not too long ago, side sleeping was said to be okay. But babies placed on their sides can easily roll onto their bellies and could have trouble breathing.

Researchers are studying the possibility that SIDS may be caused by problems with how well the brain controls breathing and/or temperature during the first few months of life.² More research on this is needed.

What are the symptoms?

SIDS has no symptoms or warning signs. Babies who die of SIDS seem healthy before being put to bed. They show no signs of struggle and are often found in the same position as when they were placed in the bed.

How is SIDS diagnosed?

SIDS is named the cause of death only when no other cause is found. To find out why a baby died, medical experts review the baby's and parents' medical histories, study the area where the baby died, and do an autopsy.

What can you do to reduce the risk of SIDS?

There is no sure way to prevent SIDS, but doing certain things may help protect a baby:³

• The most important thing you can do is to always place your baby to sleep on his or her back rather than on the stomach or side.
• Don't smoke while you are pregnant. Also, do not let anyone smoke around your baby after he or she is born.
• For the first 6 months, have your baby sleep in a crib in the same room where you sleep.
  • Make sure the baby sleeps on a firm mattress (with a fitted sheet).
  • Don't put anything in the crib that a baby can pull over his or her head, such as blankets, comforters, stuffed toys, or pillows.
  • If you use bumper pads, use ones that are thin and firm, and make sure they are attached tightly to the crib.
  • Keep the room warm enough so that your baby can sleep in lightweight clothes without a blanket.
• Consider offering your baby a pacifier at nap time and bedtime. This may help prevent SIDS, though experts do not know why. If you breast-feed, wait until your baby is about a month old before you start giving him or her a pacifier.