Experts answer the three most common questions parents have about SIDS, or sudden infant death syndrome.

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If you're a parent, you've likely heard horror stories of families losing babies in their sleep, a cause of death referred to as SIDS (Sudden Infant Death Syndrome). The acronym represents every parent's worst nightmare, and has led many families searching for tools to help them prevent it.

While SIDS cases are rare (according to the CDC, in 2017 there were 1,700 deaths due to SIDS), it may leave you wondering what is SIDS and how is it caused. We gathered expert insight and the latest research to answer your questions about SIDS:

What is SIDS?

Sudden Infant Death Syndrome (SIDS) is defined by the American Academy of Pediatrics (AAP) define Sudden Infant Death Syndrome as an infant death which cannot be explained after a thorough case investigation, including a scene investigation, autopsy, and review of clinical history. Due to the sudden and unexplained nature of SIDS, it is a common concern and worry for parents.

What are the symptoms of SIDS?

"Unfortunately, there are no preceding symptoms of SIDS, which is why attending to preventative factors is so important.," says William Mudd, DO, pediatrician at Cleveland Clinic Children's.

However, if a baby is found with the following criteria, it may be due to SIDS.

"The majority of infants will be less than 6 months of age and be found unresponsive, cool, or with dusky gray and blue color changes after they were put to sleep," says Melissa Manrique, MD, pediatric hospitalist at Lurie Children's at Northwestern Medicine Central DuPage Hospital.

According to one study, sweating may also be a symptom of SIDS in the days and weeks before SIDS.

What causes SIDS?

Sudden Infant Death Syndrome causes are still not fully understood by pediatricians and researchers. However, there are a few things they believe may lead to SIDS. Here's a look at each of them:

Brain Defects.

"It appears that SIDS may be associated with defects in the portion of the brain related to breathing and arousal from sleep," says Dr. Mudd. One study found that 40% of infants who died from SIDS had an abnormality in the hippocampus.

A 2017 study also found that SIDS may be due to an abnormality in the brain chemical serotonin.

Biological Factors

One study found that babies born premature or who have low birth weight have up to four times the risk of SIDS than those infants born at term.

Respiratory Infection

A 2005 study found that SIDS may be due to an overwhelming pro-inflammatory response to bacterial toxins.


"We tend to see a genetic link as infants who have siblings affected with SIDS are at a higher risk," adds Dr. Mudd. A 2018 study found that a genetic mutation in the gene SCN4A may contribute to SIDS.

Environmental and Behavioral Components

"Research shows that environmental risks such as exposure to second hand cigarette smoke; presence of blankets or stuffed animals, ill-fitting crib mattresses allowing for crevices infants can fall into and sleeping on soft surfaces such as fluffy comforters or waterbeds; laying an infant on her stomach to sleep; and parents co-sleeping in the same bed all contribute to increased risk of SIDS," says Dr. Mudd.

And this includes a child's clothing. "When an infant wears too many clothes to sleep, this also increases risk," says Dr. Manrique.

Furthermore, SIDS is more common in winter. A 2009 study reported that incidence of SIDS increases in winter, and it may be due to an increased susceptibility to infections. It may also be due to extra blankets and clothing that may cause overheating.