Family Health Guide

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SIDS: Risk Factors

There are no causes of SIDS, by definition. If a diagnostic cause is found, then it’s not SIDS, but an explained SUID. What we do know, though, is that there are risk factors linked to the condition:

  • Stomach and side sleeping:  Babies who sleep on their stomachs or sides face the biggest danger: They have twice the risk of dying from SIDS as babies who sleep on their backs (babies who sleep on their sides can roll onto their bellies). One theory is that when a baby's face is turned toward the mattress, he's re-breathing the carbon dioxide he exhales, which limits the amount of oxygen he takes in.  In 1992, the American Academy of Pediatrics (AAP) recommended that infants be placed face-up for sleep.  The Back to Sleep campaign was launched in 1994, and the SIDS rate declined by more than half over the next 10 years.
  • Brain irregularities:  A study from Children's Hospital Boston found that some babies who die from SIDS have irregularities in their brain stem; the region may not process the neurotransmitter serotonin properly, which can interfere with their ability to regulate body temperature, as well as wake up enough to turn their head if they’re having trouble breathing while sleeping. If that arousal center isn't functioning properly, a baby sleeping in a position that limits his oxygen may not wake up in time. This helps explain why SIDS rates drop significantly after six months and disappear almost entirely at one year; The brain stem continues to mature, and even abnormal brain stems are eventually able to process serotonin appropriately.
  • Genetic anomalies: Researchers are also looking into undiagnosed genetic anomalies that cause no symptoms but are ultimately fatal. A metabolic disorder called MCAD (medium chain acyl-CoA dehydrogenase deficiency), for instance, impairs the baby's ability to process fatty acids, eventually causing a sudden and fatal interruption in heart function. Some states test for MCAD as part of their routine metabolic screening. Another condition is long QT syndrome, a rare electrical disorder in the heart that causes sudden bursts of extremely rapid heartbeats and can lead to cardiac arrest. MCAD and long QT syndrome account for fewer than 15 percent of SIDS cases , but  mothers who have had a family history of MCADD should ask about having their babies screened, either pre- or post-natally.

Some preliminary research also suggests that babies who begin daycare or who are put in the care of someone other than a parent before 4 months of age may be at increased risk as well if they put the baby to sleep on their stomach.  The majority of daycare workers are aware of the Back to Sleep recommendation, but clearly some are not, since more than 20 percent of daycare centers still put babies to sleep on their tummies. 

Of course, this doesn’t mean you shouldn’t put your baby in daycare if you need to. It only means that you have to be firm with any caregivers—whether a daycare center worker or your mother-in-law—about safe-sleeping practices. And, of course, look for a licensed daycare facility, something you’d want to do anyway for many other reasons.