Health Library

Sudden Infant Death Syndrome (SIDS)

Causes of SIDS

Despite 30 years of research, experts have not yet found an exact cause for SIDS.

Research has shown that some babies who die from SIDS had brain abnormalities that made them more at risk for sudden death during infancy. These studies found abnormalities in the "arcuate nucleus,” the part of the brain that helps control breathing and blood pressure. Babies born with defects in other parts of the brain or body may also be more prone to SIDS. These abnormalities may result from the fetus’ exposure to toxins or decreases in oxygen during pregnancy.

It’s normal for babies to sense when they do not get enough oxygen while sleeping. Their brain triggers them to wake and cry, which changes their heart rate and breathing patterns to increase the amount of oxygen they take in. Babies are at an increased risk for SIDS if they do not inhale enough oxygen or if they inhale too much carbon dioxide.

Some babies affected by SIDS have had an increased number of immune system cells and proteins. These cells and proteins can cause the brain to change the baby’s heart rate and breathing during sleep, or can put the baby into a deeper sleep. Many babies who have died from SIDS have had respiratory infections prior to their deaths. More SIDS cases occur during the colder months of the year, when respiratory and intestinal infections are more common.

Metabolic disorders, such as medium chain acyl-CoA dehydrogenase deficiency, can also put a baby at an increased risk of SIDS. This disorder prevents the baby from processing fatty acids the right way. Over time, a buildup of acid metabolites can lead to issues with breathing and heart function. If there is a family history of metabolic disorders or childhood deaths of unknown cause, genetic screening of the parents can be completed. If one or both parents are found to be a carrier for metabolic disorders, the baby can be tested soon after birth.

Risk Factors for SIDS

In the United States, there are about 1,300 babies who die of SIDS each year. Some babies are more at risk than others. SIDS is most likely to occur between 1 and 4 months of age. Factors that may place a baby at higher risk of SIDS include:

• Babies who sleep on their stomachs
• Mothers who smoke when they are pregnant
• Babies who are around people who smoke
• Mothers who are younger than 20 years old at the time of their first pregnancy
• Babies born to mothers who had no or late prenatal care
• Premature or low birth weight babies

Diagnosis of SIDS

The diagnosis of SIDS is given when a cause of infant death cannot be explained, even after a thorough investigation. This includes an autopsy, examination of the death scene, a review of illnesses the baby had prior to death, and any other pertinent medical history.

Methods to Decrease the Risk of SIDS

Though there is no way to predict or prevent SIDS, research has found some things that can help reduce the risk of SIDS. Here are a few things you can do to lower your baby’s risk of SIDS:

Early and routine prenatal care

• Routine check-ups starting early in pregnancy, proper nutrition, and avoidance of smoking, drugs and/or alcohol may prevent your baby from developing an abnormality that increases risk for SIDS. This may also reduce the chance of having a premature or low birth weight baby.

Back to sleep

• Studies have shown that placing babies on their backs to sleep has reduced the number of SIDS cases by as much as half in countries where it was previously common for babies to sleep on their stomachs.
• Parents and other caregivers should put babies to sleep on their backs. You should not put them on their stomachs or sides. Babies who can roll from their back to their belly and from their belly to their back on their own can be left in that position.
• If your baby falls asleep in a car seat, stroller, swing, infant sling or infant carrier, move them to a crib or bassinet as soon as you are able.
• Though many parents worry babies will choke on spit-up or vomit if placed on their backs for sleep, studies have not found any proof of increased risk of choking or other problems.

Place your baby on their stomach while awake

• Tummy time while your baby is awake and supervised is important for motor development.
• Time spent on the stomach while awake may help prevent flat spots from forming on the back of your baby's head. This is most often temporary and will return to normal soon after your baby starts to sit up.

Proper bedding

• Put your baby to sleep on a firm mattress or other firm surface such as a crib, bassinet, portable crib or play yard.
• Do not use fluffy blankets or comforters under your baby.
• Do not let your baby sleep on an adult bed (especially waterbeds), sofas, chairs, sheepskin, pillows or other soft fabrics.
• Do not place soft stuffed toys, bumper pads or pillows in the crib with your baby. Some babies have been smothered by these soft materials in their crib.
• You can check with the Consumer Product and Safety Commission website at www.cpsc.gov for more information about crib safety standards.

Temperature control

• Your baby should be kept warm, but not too warm during sleep. Do not overdress your baby.
• An overheated baby is more likely to go into a deep sleep and may be hard to wake up.
• Keep your baby’s room at a temperature that feels comfortable to you.

Avoid bed-sharing

• Room-sharing, not bed-sharing, is advised. Studies show this decreases the risk of SIDS by as much as 50%. These studies show that bed-sharing can alter sleep patterns of the adult and baby.
• Devices that claim to make bed-sharing “safe,” such as co-sleepers or positioners, are not advised.
• If a parent chooses to sleep in the same bed with their baby, even though this is not advised, care should be taken to avoid using soft sleep surfaces. Quilts, blankets, pillows, comforters or other soft materials should not be placed under the baby.
• Unlike cribs, which must meet safety standards for babies, adult beds are not made for babies. They increase the risk that your baby could be trapped and suffocated.

Smoke-free environment

• Do not smoke during pregnancy.
• Keep your home and car smoke-free to protect your baby. Do not allow others to smoke around your baby.
• Babies and young children exposed to smoke have an increased risk of SIDS.

Pediatric healthcare

• If your baby seems sick, call your doctor or clinic right away.
• Take your baby for routine check-ups and immunizations. Claims that immunizations increase the risk of SIDS are not supported by research. Babies who receive scheduled immunizations are less likely to die of SIDS.
• If your baby has an event where they stop breathing and turn blue or limp, even if they resume breathing on their own, bring them to the emergency room immediately to determine the cause.

Breastfeed your baby

• If able, breastfeed your baby. A few studies have found SIDS to be less common in babies who have been breastfed. Breast milk may provide protection from some infections that can trigger sudden death in babies.
• If you bring your baby into your bed to feed or comfort them, put your baby back in their crib when you are ready to return to sleep.

Consider a pacifier at bedtime and nap time

• Studies have shown a protective effect of pacifiers on reducing the risk of SIDS. Offer a pacifier to your baby when you put them down to sleep. If the pacifier falls out of their mouth, you don’t have to put it back once they fall asleep.
• Do not hang the pacifier around your baby’s neck or attach it to clothing while your baby is sleeping. This could strangle or injure your baby.

Home monitors

• Though some electronic home monitors can detect and sound an alarm when a baby stops breathing, there is no proof that these can prevent SIDS. In 1986, the National Institutes of Health advised that home monitors should not be used for babies who do not have an increased risk of sudden, unexpected death.
• The monitors may be advised for:
  • Babies who have had one or more severe events during which they stopped breathing and needed resuscitation or stimulation
  • Premature babies with apnea (stopping breathing)
  • Siblings of two or more babies affected by SIDS
• If an event has occurred, or if a baby is on a monitor, parents need to know how to properly use and maintain the device. They also need to know how to resuscitate their baby if the alarm sounds.

Ensure that other caregivers, babysitters, family members and day care centers understand: 

• SIDS 
• Risk factors
• What they can do to prevent SIDS

Related Links

Please see these resources for more information about Sudden Infant Death Syndrome (SIDS):

• The National Institute of Child Health and Human Development Safe to Sleep Public Education Campaign
• Book: The Death of Innocents, by Richard Firstman and Jamie Talan

Research Studies

• The Journal of the American Medical Association (JAMA): Cardiorespiratory Events Recorded on Home Monitors