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Sudden Infant Death Syndrome (SIDS)


Christopher P. Raab

, MD, Sidney Kimmel Medical College at Thomas Jefferson University

Last full review/revision Oct 2019| Content last modified Oct 2019

Sudden infant death syndrome is the sudden, unexpected death, usually during sleep, of a seemingly healthy infant 1 year of age or younger.

  • The cause of sudden infant death syndrome (SIDS) is not known.
  • Putting infants to sleep on their back; removing pillows, bumper guards, and toys from the crib; protecting infants from overheating; and preventing infants from breathing second-hand cigarette smoke may help prevent SIDS.
  • Parents who have lost a child to SIDS should seek counseling and support groups.

Although sudden infant death syndrome (SIDS; also called crib death) is rare overall in the United States (about 1 in 1,000 births), it is one of the most common causes of death in infants between the ages of 2 weeks and 1 year. African American and Native American children have twice the average risk of SIDS. It most often affects children between the second month and fourth month of life. The syndrome occurs worldwide. There are many risk factors.

Risk factors for sudden infant death syndrome

Children who have or who are exposed to any of the following risk factors are at increased risk of SIDS:

  • Sleeping on the stomach (most important risk factor)
  • African American or Native American ethnicity
  • Brother or sister died of SIDS
  • Cold temperatures/winter months
  • Growth failure
  • Low birth weight
  • Low-income family
  • Male sex
  • Mother has had many pregnancies
  • Mother under age 20
  • Mother smoked or used drugs during pregnancy
  • No pacifier
  • Old or unsafe crib
  • Overheating (caused by blankets or a hot room)
  • Pauses in breathing (apnea) that required resuscitation
  • Poor prenatal care
  • Prematurity
  • Recent illness
  • Sharing a bed with a parent or caretaker (bed-sharing or co-sleeping)
  • Short amount of time between pregnancies
  • Single mother
  • Smoking in the home
  • Soft bedding
  • Upper respiratory tract infection
  • Waterbed mattress


The cause of sudden infant death sydrome (SIDS) is unknown. It may be due to an abnormality in the control of breathing. Some infants with SIDS show signs of having had low levels of oxygen in their blood and having had periods when they stopped breathing (called apnea).

Laying infants down to sleep on their stomach and the use of soft bedding (such as pillows and lamb’s wool blankets) have been linked to SIDS. Sleeping together with an infant on a sofa, cushion, or bed (see Co-sleeping) also increases the risk of SIDS.

Did You Know...

  • Although rare, sudden infant death syndrome (SIDS) is one of the most common causes of death in infants between the ages of 2 weeks and 1 year. It is associated with laying infants down to sleep on their stomach.


  • Autopsy

Doctors cannot make the diagnosis of SIDS without an autopsy (an inspection and examination of a body after death) to rule out other causes of sudden, unexpected death (such as intracranial hemorrhage, meningitis, or myocarditis).

Doctors also need to assess whether the infant suffocated or died as the result of abuse.


  • Putting infants to sleep on their back

Despite the known risk factors for SIDS, there is no certain way to prevent it. However, certain measures seem to help, particularly putting infants to sleep on their back on a firm mattress. The number of SIDS deaths has decreased dramatically as more parents have put their infants to sleep on their back (see the Safe to Sleep® campaign). Parents should also remove pillows, bumper guards, and toys that could block an infant's breathing. Avoiding overwrapping and protecting infants from overheating may also help. Breastfeeding and preventing infants from breathing second-hand cigarette smoke may help and clearly have other health benefits.

There is no evidence that at-home breathing monitors reduce the risk of SIDS.

Safe to Sleep: Reducing the Risk of Sudden Infant Death Syndrome

  • Position: Always place the infant on the infant’s back to sleep, for naps and at night.
  • Surface: Place the infant on a firm sleep surface, such as a safety-approved crib mattress, covered by a fitted sheet.
  • Bedding: Keep soft objects, toys, blankets, and other loose bedding out of the infant’s sleep area.
  • No smoking: Do not allow smoking around the infant. Not smoking during pregnancy is also important.
  • Location: Set up the infant’s sleep area close to but separate from the sleep area of the parents and other children.
  • Pacifiers: Consider offering the infant a clean, dry pacifier when placing the infant down to sleep.
  • Temperature: Do not let the infant overheat during sleep.

Home monitors and products that claim to prevent sudden infant death syndrome do not seem helpful.

To help prevent flat spots from developing on the infant's head, infants should spend some time on their tummy when they are awake and someone is watching them. To help make the infant's head round, parents should change the direction that the infant lies in while in the crib each week and avoid leaving the infant for too long in car seats, carriers, and bouncers.

Adapted from The National Institute of Child Health and Human Development (Safe to Sleep® campaign).

Resources for Parents Who Have Lost an Infant to SIDS

  • Counseling
  • Support groups

Most parents who have lost an infant to SIDS are grief-stricken and unprepared for the tragedy. They usually feel guilty. They may be further traumatized by investigations conducted by police, social workers, or others. Counseling and support from specially trained doctors and nurses and other parents who have lost an infant to SIDS are critical to helping parents cope with the tragedy. Specialists can recommend reading materials, web sites (visit, and support groups to assist parents.

More Information

  • Safe to Sleep® campaign
  • American SIDS Institute

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