What is SIDS?

SIDS, or Sudden Infant Death Syndrome, is defined as the sudden and unexpected death of any infant or young child under one year of age that remains unexplained after a complete investigation, which includes an autopsy, examination of the death scene, and review of the symptoms or illnesses the infant had prior to dying and any other pertinent medical history.  Because most cases of SIDS occur when a baby is sleeping in a crib, SIDS is also commonly known as crib death.

SIDS is the leading cause of death in infants between 1 month and 1 year of age.  Most SIDS deaths occur when a baby is between 1 and 4 months of age.  More boys are SIDS victims than girls.

What causes SIDS?

Some facts about SIDS:

There is no way to completely prevent SIDS.

The peak period for SIDS is between two and four months old. It is very rare before one month of age, and at least 95 percent of all the cases have occurred before children reach six months old.

SIDS is more common in boys than in girls (About 60% are Boys).

Putting children to sleep on their backs lowers the risk of SIDS by about three times.

Mothers who smoke during pregnancy are three times more likely to have a SIDS baby, and exposure to passive smoke from smoking by mothers, fathers, and others in the household doubles a baby's risk of SIDS.

Mounting evidence suggests that some SIDS babies are born with brain abnormalities that make them vulnerable to sudden death during infancy.  Studies of SIDS victims reveal that many SIDS infants have abnormalities in the "arcuate nucleus," a portion of the brain that is likely to be involved in controlling breathing and waking during sleep.  Babies born with defects in other portions of the brain or body may also be more prone to a sudden death.  These abnormalities may stem from prenatal exposure to a toxic substance, or lack of a vital compound in the prenatal environment, such as sufficient oxygen.  Cigarette smoking during pregnancy, for example, can reduce the amount of oxygen the fetus receives.

Scientists believe that the abnormalities that are present at birth may not be sufficient to cause death.  Other possibly important events occur after birth such as lack of oxygen, excessive carbon dioxide intake, overheating or an infection.  For example, many babies experience a lack of oxygen and excessive carbon dioxide levels when they have respiratory infections that hamper breathing, or they rebreathe exhaled air trapped in underlying bedding when they sleep on their stomachs.  Normally, infants sense such inadequate air intake, and the brain triggers the babies to wake from sleep and cry, and changes their heartbeat or breathing patterns to compensate for the insufficient oxygen and excess carbon dioxide.  A baby with a flawed arcuate nucleus, however, might lack this protective mechanism and succumb to SIDS.  Such a scenario might explain why babies who sleep on their stomachs are more susceptible to SIDS, and why a disproportionately large number of SIDS babies have been reported to have respiratory infections prior to their deaths.  Infections as a trigger for sudden infant death may explain why more SIDS cases occur during the colder months of the year, when respiratory and intestinal infections are more common.

The numbers of cells and proteins generated by the immune system of some SIDS babies have been reported to be higher than normal.  Some of these proteins can interact with the brain to alter heart rate and breathing during sleep, or can put the baby into a deep sleep.  Such effects might be strong enough to cause the baby's death, particularly if the baby has an underlying brain defect.

Some babies who die suddenly may be born with a metabolic disorder.  One such disorder is medium chain acylCoA dehydrogenase deficiency, which prevents the infant from properly processing fatty acids.  A build-up of these acid metabolites could eventu ally lead to a rapid and fatal disruption in breathing and heart functioning. If there is a family history of this disorder or childhood death of unknown cause, genetic screening of the parents by a blood test can determine if they are carriers of this disorder.  If one or both parents is found to be a carrier, the baby can be tested soon after birth.

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