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Sudden Infant Death Syndrome (SIDS)

What is Sudden Infant Death Syndrome (SIDS)?

Sudden infant death syndrome (SIDS) is the sudden and unexplained death of a baby under 1 year of age. It is the major cause of death in babies from 1 month to 1 year of age. The death is sudden and can't be predicted. In most cases, the baby seems healthy.

Death happens quickly, most often during a sleep time.

Causes of SIDS

After 30 years of research, experts still cannot find any exact cause for SIDS. Though there is no way to predict or prevent SIDS, research has found some things that can help reduce the risk of SIDS.

Research has shown that some babies who die from SIDS have brain abnormalities that make them more at risk for sudden death during infancy. Studies of SIDS victims show that many have abnormalities in the "arcuate nucleus." This is a part of the brain that likely helps control breathing and waking during sleep. Babies born with defects in other parts of the brain or body may also be more prone to a sudden death. These abnormalities may result from the fetus being exposed to toxins or a decrease in oxygen. One reason for decreased oxygen to a fetus is cigarette smoking.

SIDS may be linked to:

  • Lack of oxygen
  • Too much carbon dioxide intake
  • Overheating
  • Infection

Lack of oxygen and high carbon dioxide levels may be due to:

  • Respiratory infections that cause breathing problems
  • Babies that sleep on their stomachs and rebreathe the air they exhale that is trapped in the bedding under them

It’s normal for babies to sense when they do not get enough air when sleeping. Their brain triggers them to wake from sleep and cry. This changes their heartbeat or breathing patterns to make up for the lowered oxygen and too much carbon dioxide, but a baby with a flawed arcuate nucleus may not be able to do this.

This may explain why:

  • Babies who sleep on their stomach are more at risk for SIDS.
  • A large number of SIDS babies have been noted to have 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.

The number of cells and proteins made by the immune system of some SIDS babies has been noted to be higher than normal. Some of these proteins can cause the brain to change heart rate and breathing during sleep, or can put the baby into a deep sleep. This might be strong enough to cause the baby's death, even more so if the baby has an underlying brain defect.

Some babies who die suddenly may be born with a metabolic disorder, such as medium chain acyl-CoA dehydrogenase deficiency. This prevents the baby from processing fatty acids the right way. A buildup of these acid metabolites could, over time, lead to a rapid and deadly problem in breathing and heart function. If there is a family history of this disorder or childhood death of unknown cause, genetic screening of the parents can be done. A blood test can find out if they are carriers of this disorder. If one or both parents are found to be a carrier, the baby can be tested soon after birth.

Risk Factors for SIDS

About 2,300 babies in the United States die of SIDS each year. Some babies are more at risk than others. For example, SIDS is more likely to occur between 1 and 4 months of age. Factors that may place a baby at higher risk of dying from SIDS include:

  • Babies who sleep on their stomachs rather than their backs
  • Mothers who smoke during pregnancy (three times more likely to have a SIDS baby)
  • Exposure to passive smoke from smoking by mothers, fathers and others in the household (doubles a baby's risk of SIDS)
  • 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 birthweight babies

Diagnosis for SIDS

The diagnosis of SIDS is given when the cause of death cannot be explained even after a complete investigation. This includes:

  • An autopsy
  • Examination of the death scene
  • Review of the symptoms or illnesses the baby had prior to dying
  • Any other pertinent medical history

Methods to Decrease the Risk of SIDS

At this time, there is no way to predict which babies will die from SIDS. There are a few things parents can do to lower the risk of SIDS, though. This includes:

Prenatal Care

  • Early and routine prenatal care
  • Routine check-ups starting early in pregnancy, proper nutrition, and no smoking or drug or alcohol use by the mother may prevent a 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, which also increases the risk for SIDS. The risk of SIDS is higher for babies whose mothers smoked when they were pregnant.

Put Your Baby on His / Her Back for Sleep

  • Parents and other caregivers should put babies to sleep on their backs. You should not put them on their stomach or side.
  • Studies have shown that placing babies on their backs to sleep has reduced the number of SIDS cases by as much as a half in countries where it was common for babies to sleep on their stomachs.
  • Babies that can roll from their back to their belly and from their belly to their back on their own can be left in that position.
  • Move your baby to a crib or bassinet as soon as you can if they fall asleep in a car safety seat, stroller, swing, infant sling or infant carrier.

Parents need to be sure that other caregivers, babysitters, family members and day care centers understand:

  • SIDS
  • SIDS risks
  • What they can do to prevent SIDS

Though many parents are afraid babies will choke on spit-up or vomit if placed on their backs, studies have not found any proof of increased risk of choking or other problems.

Use Other Positions Only If the Doctor Tells You To

In some cases, doctors may say that a baby should be placed on their stomach to sleep if they have a disorder such as gastroesophageal reflux or certain upper airway disorders. These disorders make them more likely to have choking or breathing problems while lying on their backs.

Place Baby on Their Stomach while Awake

A certain amount of tummy time while the baby is awake and being watched is advised for motor development of the shoulders. Also, awake time on the stomach may help prevent flat spots from forming on the back of the baby's head. This is most often temporary and will return to normal soon after the baby starts to sit up.

Proper Bedding

Make sure that your baby sleeps 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 the baby. Do not let the 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 for more information about crib safety standards.

Temperature Control

Babies should be kept warm, but they should not be allowed to get too warm. An overheated baby is more likely to go into a deep sleep and be hard to wake up. The temperature in the baby's room should feel comfortable to an adult. Do not overdress the baby. Keep the temperature in your baby's room so that it feels comfortable to you.

Avoid Bed Sharing

Room-sharing but not bed-sharing is advised. Studies show this decreases the risk of SIDS as much as 50 percent. These studies show that bed sharing between mother and baby, and others, can alter sleep patterns of the mother and her baby. Devices which claim to make bed-sharing “safe” such as co-sleepers or positioners are not advised, care should be taken to avoid using soft sleep surfaces. If a mother chooses to sleep in the same bed with her 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. Do not smoke or use substances such as alcohol or drugs, which may make it hard for you to wake up. Unlike cribs, which are made to meet safety standards for babies, adult beds are not made for a baby. They may carry a risk of your baby being trapped and suffocated on accident.

Smoke-Free Environment

Do not smoke when you are pregnant and do not allow others to smoke around your baby. Keep all of your home, your car, and other vehicles smoke-free to protect your baby. Babies and young children exposed to smoke have more colds and other disease, as well as an increased risk of SIDS.

Pediatric Healthcare

If your baby seems sick, call your doctor or clinic right away. Parents should take their babies for routine well baby check-ups and immunizations. Claims that immunizations increase the risk of SIDS are not proven by research. Babies who receive their scheduled immunizations are less likely to die of SIDS. If a baby ever has an event where they stop breathing and turn blue or limp, the baby should be checked by a doctor to figure out the cause.

Breastfeed Your Baby

If able, you should breastfeed your baby. Research suggests that breastfeeding might reduce the risk of SIDS. A few studies have found SIDS to be less common in babies who have been breastfed. This may be because breast milk can 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. You don’t have to put the pacifier back in once the baby falls 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. If you are breastfeeding, wait until feeding is going well before giving your baby a pacifier; this may take several weeks.

Home Monitors for Babies at Risk

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 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 SIDS babies

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.

Related Resources

Please see these resources for more information about sudden infant death syndrome (SIDS).

Research Studies

Studies that have compared healthy infants with those at increased risk for sudden infant death syndrome (SIDS) have shown:

  • Events such as apnea and below-normal heart rate are common, even in healthy term infants.
  • Extreme cardiorespiratory events are common only in preterm infants. Their timing suggests they are not likely to be immediate precursors of SIDS.

Last Updated 07/2021

Reviewed By Kelli Harding, RN

Visiting Cincinnati Childrens.

Cincinnati Children’s has primary care services at locations throughout Greater Cincinnati.