What are the Causes of SIDS?

Just hearing the term "SIDS" can cause anxiety in some parents. Sudden infant death syndrome (SIDS), also called "crib death," affects about 3,400 babies a year. Understanding the reasons why some babies die unexpectedly in their sleep can help in reducing the risk of SIDS.

We spoke with pediatrician Dr. Carmela Sosa to explain potential causes and offer ways to prevent a tragedy from happening to families.

What is SIDS?

SIDS is the sudden and unexplained death of a baby, according to Mayo Clinic. It can only be reported as the cause of death if no other cause is found.

"One of the challenges in identifying the precise cause of SIDS is there's no single test, or group of tests such as blood tests or x-rays, that will tell us which infant will succumb to SIDS," explains Dr. Sosa.

SIDS is the leading cause of death in a baby younger than one year. Those who are between the ages of 1 and 4 months have a higher risk, but SIDS is less common in babies older than eight months. Parents should practice safe sleep habits until a baby turns a year old.

What are the risk factors for SIDS?

Some factors increase the risk of SIDS, according to the Safe to Sleep campaign. Some things you have control over, and some you don't.

Sleeping environment

Sleep position and the environment your baby sleeps in affect SIDS risk. You can change these factors to make sleeping safer.

Putting your baby on their side increases the risk of SIDS. Sleeping in a warm room, dressing your baby too warm or placing them on their stomach can cause babies to overheat.

Soft bedding and using blankets, crib bumpers, and stuffed animals increases SIDS risk as well as their chance of suffocating or becoming trapped in bedding if blankets wrap around your baby's head.

Maternal factors

There are things you, as the parent, can do to lower your baby's chance of SIDS, such as getting regular prenatal care. Smoking, alcohol and substance use can increase the risk of SIDS for babies.

Infant factors

These are factors you can't control. Babies who weigh less than 5 pounds 8 ounces or are born premature—meaning before 37 weeks—have an increased risk for SIDS. Biological sex also plays a role. About 60% of babies who have died of SIDS are male, versus 40% of females.

What are the potential causes of SIDS?

"There's a common misperception that SIDS deaths are due to suffocation. The actual cause of SIDS is still unknown—though we're gaining insights through research," says Dr. Sosa.

Problems that involve the brain

The brainstem—part of the brain that connects to the spinal cord—is responsible for certain bodily functions. According to Dr. Sosa, these include controlling heart rate, breathing, and sleep. If there's a concern in the brain stem, the signals telling a baby to breathe while sleeping can be cut off, causing them to stop breathing.

Another problem in the brain involves the neurotransmitter serotonin. Serotonin plays a role in mood but can also affect the body's involuntary functions, such as breathing. Some studies have pointed to serotonin as a possible cause of SIDS.

Another chemical researchers are studying for SIDS risk is butyrylcholinesterase (BChE). "BChE is part of an enzyme system that plays a role in neurotransmission in the autonomic, or involuntary, nervous system. Post-mortem testing has shown lower levels of BChE enzyme activity in infants who died of SIDS," explains Dr. Sosa.

Problems with breathing during sleep

Dr. Sosa says infants undergo incredible change in the first 6 to 12 months of life, including their sleep patterns. Babies have different sleep states than adults, referred to as active sleep and quiet sleep. These are the very early REM and non-REM stages. The quiet sleep state can decrease a baby's blood pressure, heart rate, and breathing.

"Arousal from sleep is a protective mechanism necessary for survival. But infants have a decreased response to arousal from sleep," explains Dr. Sosa.

Problems with genetics

"With the recent introduction of genetic technologies that can look at whole genomes, we recognize genetics may play a role in some SIDS cases. Several studies have looked at SIDS and found gene mutations may predispose infants to death, though they are not likely solely responsible," explains Dr. Sosa.

How can you lower the risk of SIDS?

Dr. Sosa says there are some measures parents can take to prevent SIDS:

• Always place your baby on their back to sleep.
• Put your baby to sleep in their own space on a firm mattress.
• Don't use any soft bedding, crib bumpers or stuffed animals.
• If possible, breastfeed your baby.
• Offer your baby a pacifier for bedtime and naps once breastfeeding is going well.
• Keep your baby away from tobacco smoke.
• Sleep in the same room as your baby. This can protect them from SIDS, but the American Academy of Pediatrics cautions against sharing a bed with your baby.
• Stop swaddling once your baby can roll over.

No one wants to think about what might happen to their baby during sleep. While certain factors, such as genetics or developmental changes, are out of our control, there are steps parents can take to make sleep as safe as possible for their babies.

Experts

• Carmela Sosa, MD, FAAP, board-certified in pediatrics