A lack of answers is partly what makes sudden infant death syndrome (SIDS) so frightening. SIDS is the leading cause of death among infants who are 1 month to 1 year old, but despite years of research and numerous studies, SIDS is still unpredictable and unpreventable. However, research into the causes of SIDS has led doctors to recommend steps parents can take to reduce the risk of SIDS in their infants. As more parents begin to follow that advice, the number of deaths from SIDS is dropping.

Searching for Answers
SIDS is frequently described as a parent's worst nightmare because it strikes without warning, usually in seemingly healthy babies. As the name implies, SIDS is the sudden and unexplained death of an infant who is younger than 1 year old. Most SIDS deaths are associated with sleep (hence the common reference to "crib death"), and infants who die of SIDS show no signs of suffering.

While most conditions or diseases usually are diagnosed by the presence of specific symptoms, SIDS is a diagnosis of exclusion, given only after all other possible causes of death have been ruled out through an autopsy, an examination of the death scene, and a complete review of the infant's medical history. These procedures help distinguish true SIDS deaths from those resulting from accidents, abuse, and previously undiagnosed conditions, such as cardiac or metabolic disorders.

When considering which babies could be most at risk, Marj Hershberger, a certified pediatric nurse practitioner, notes that no single risk factor is likely to be sufficient to cause a SIDS death. Rather, several risk factors combined may contribute to cause an at-risk infant to die of SIDS.

According to the National Institute of Child Health and Human Development (NICHD), the incidence of SIDS is greatest in infants younger than 6 months of age and increases during cold weather. African-American infants are two times more likely to die of SIDS than white infants, and Native Americans are about three times more likely than whites. More boys than girls fall victim to SIDS. Other potential risk factors include:

• smoking, drinking, or drug use during pregnancy
• poor prenatal care
• prematurity or low birth-weight
• mothers younger than 20
• smoke exposure following birth
• stomach sleeping

Foremost among the risk factors, however, is stomach sleeping. Numerous studies from Europe and Australia found a higher incidence of SIDS among babies placed on their stomachs to sleep than among those on their backs or sides. Some researchers have hypothesized that stomach sleeping puts pressure on the child's jaw, therefore narrowing the airway and hampering breathing.

Another theory is that stomach sleeping can increase an infant's risk of "rebreathing" his own exhaled air, particularly if the infant is sleeping on a soft mattress or with bedding, stuffed toys, or a pillow near his face. In that scenario, the soft surface could create a small enclosure around the baby's mouth and trap exhaled air. As the baby breathes exhaled air, the oxygen level in his body drops and carbon dioxide accumulates. Eventually, this lack of oxygen could contribute to SIDS.

Also, infants who succumb to SIDS may have an abnormality in the arcuate nucleus, a part of the brain that may help control breathing and awakening during sleep. If a baby is breathing stale air and not getting enough oxygen, the brain usually triggers the baby to wake up and cry. That movement changes the breathing and heart rate, making up for the lack of oxygen. But a problem with the arcuate nucleus could deprive the baby of this involuntary reaction and put him at greater risk for SIDS.

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