Sudden infant death syndrome (SIDS) is the sudden, unexplained death of an infant younger than one year old. Some people call SIDS "crib death" because many babies who die of SIDS are found in their cribs.

SIDS is the leading cause of death in children between one month and one year old. Most SIDS deaths occur when babies are between two months and four months old. Although health care professionals don't know what causes SIDS, they do know ways to reduce the risk. These include

• Placing babies on their backs to sleep, even for short naps - "tummy time" is for when babies are awake and someone is watching
• Using a firm sleep surface, such as a crib mattress covered with a fitted sheet
• Keeping soft objects and loose bedding away from sleep area
• Making sure babies don't get too hot - keep the room at a comfortable temperature for an adult

Sudden infant death syndrome (SIDS)

Introduction

Sudden infant death syndrome (SIDS) is the sudden and explained death of a seemingly healthy baby.

Typically, a peacefully sleeping baby simply never wakes up. In most cases, no cause is ever found. Most SIDS deaths occur in children who are between 2 months and 4 months old. Sudden infant death syndrome rarely occurs before 1 month of age or after 6 months.

Although the exact cause of sudden infant death syndrome is still unknown, researchers have discovered some factors that may put babies at risk. They've also identified simple measures you can take to help protect your child from sudden infant death syndrome. Perhaps the most important is placing your baby to sleep on his or her back.

Causes

Over the years, researchers have investigated and ruled out a number of possible causes of sudden infant death syndrome, including suffocation, vomiting or choking, birth defects, metabolic abnormalities, and infection.

Exactly why SIDS occurs remains elusive, but many experts believe there are probably multiple factors that cause SIDS. For example, it's likely that an infant must have some sort of biological vulnerability, such as a heart or brain defect, combined with an environmental stressor, such as stomach sleeping, before SIDS can occur.

These things must also occur during a critical developmental period in the baby's life, typically during the first six months. These three factors - vulnerability, critical developmental period and outside stressor - combine to form what's known as the triple-risk model.

Research offers clue

In 2006, researchers discovered that abnormalities in a part of the brain that helps control breathing and arousal likely play a role in SIDS. Other research has focused on the way babies breathe while they're asleep - especially their response to low blood oxygen levels (hypoxia) - and on heart function.

Researchers are also continuing to investigate the link between SIDS and long QT syndrome, a subtle electrical disturbance in the heart that causes sudden, extremely rapid heart rates. A 2007 study found that almost one in 10 babies who died of SIDS had a genetic defect in one of the genes responsible for long QT syndrome. If you have a history of SIDS in your family, your doctor will want to check for the presence of long QT syndrome in your infant. This can usually be done withanelectrocardiogram (ECG) and confirmed, if necessary, with genetic studies.

One thing that is known is that childhood immunizations don't play a role in sudden infant death syndrome. After reviewing the available evidence in 2005, the American Academy of Pediatrics concluded that vaccines don't increase the risk of sudden infant death syndrome.