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Sudden Infant Death Syndrome (SIDS) and Sleep

Danielle Pacheco

Written by

Danielle Pacheco, Staff Writer

Dr. Nilong Vyas

Medically Reviewed by

Dr. Nilong Vyas, Pediatrician

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Sudden infant death syndrome (SIDS) is defined as “the sudden and unexpected death of an infant under 12 months of age that remains unexplained after a review of the clinical history, complete autopsy and death scene investigation.” Also known as crib death or cot death, SIDS is part of a larger subset of conditions known as sudden unexpected infant death (SUID).

Roughly 1,360 deaths were attributed to SIDS in 2017. Most of these deaths occurred between the ages of one and six months. While its specific cause is largely unknown, parents can reduce the risk of SIDS by preparing and maintaining a safe sleeping area for their infant. Read on to learn more about SIDS and how you can ensure the utmost safety for your sleeping infant.

SIDS Risk Factors

Recent studies suggest the following factors can put infants at greater risk of SIDS:

  • Side or stomach sleeping: Researchers have established a strong link between SIDS and sleeping position. The prone (stomach) and side positions increases the risk of hypercapnia, the buildup of carbon dioxide, and hypoxia, a deficiency of oxygen in the body’s tissue. Additionally, stomach sleeping can decrease the infant’s rate of heat loss and elevate their body temperature, causing them to overheat, and also affect how their cardiovascular system functions. The side sleeping position is considered just as dangerous, and infants are more likely to roll onto their stomachs when resting on their sides. Current guidelines recommend placing infants in the supine (back sleeping) position until they reach one year. This includes nightly sleeping and daytime naps.
  • Age: Infants younger than six months old represent roughly 90 percent of all SIDS-related deaths. It’s believed the risk of SIDS peaks between one and four months. Additionally, preterm infants with low birth weights are considered at higher risk of SIDS. Consistent back sleeping is considered especially important for preterm infants.
  • Sleep environment: Per current guidelines for parents and caregivers, infants should sleep on firm, flat surfaces covered in fitted sheets. The baby’s sleep area should not contain any soft blankets, pillows, toys, or bumper pads. A significant percentage of infants who die from SIDS are found with their heads covered by bedding items. Parents should also ensure there are not any gaps between the edge of the mattress and the crib; two fingers is considered the standard rule-of-thumb.
  • Bed sharing: While common practice for parents, sharing a bed with an infant is discouraged because adult beds are not optimized for child safety. The link between co-sleeping and SIDS is still under review, but this can increase the child’s risk of strangulation, falling, and other hazards. Many adult mattresses are also outfitted with soft bedding, blankets or quilts that could cover the infant’s head, and other materials that increase the risk of SIDS. However, parents are encouraged to share a bedroom with their infant while they sleep in a crib or bassinet. SIDS can occur suddenly and infants often make little to no noise, so sharing a room allows parents to keep an eye on their little one throughout the night. Parents should consider sharing a bedroom with their baby for at least the first six months, and up to one year if possible.
  • Tobacco: Nearly every major epidemiologic study involving SIDS has pinpointed smoking as a major risk factor. This includes expectant mothers smoking while pregnant; according to some studies, up to one-third of SIDS-related deaths could be prevented if mothers completely avoided smoking throughout their pregnancy. Exposing newborns and infants to cigarette smoke is also potentially dangerous. The risk of SIDS is particularly high for infants who share a bed with someone who smokes, even if they don’t smoke while in bed.
  • Alcohol: Consuming alcohol while pregnant can increase the risk of SIDS for infants after they are born, some studies have shown. This includes alcohol use during the periods immediately prior to and following conception, as well as the first trimester.
  • Feeding: Babies who breastfeed are considered at lower risk for SIDS than those who do not drink breast milk. The risks are also lower for babies who are exclusively breastfed compared to those whose breast milk diet is supplemented with formula or solid food. Mothers should not breastfeed on chairs, sofas, and other upright surfaces where they could potentially fall asleep, as this is a suffocation risk for babies.

Some SIDS risks are suspected, but have not been studied extensively enough to draw a firm conclusion. For instance, studies have identified poor bedroom ventilation as a potential risk factor for SIDS, but more research is needed regarding this topic.

Other risk factors have been largely debunked. One prominent example is vaccines. Many infants receive several vaccines within the first six months of their life, when SIDS is most likely to occur. A wave of SIDS deaths occurred in the late 1970s, and at the time some suspected the deaths were related to the diphtheria-tetanus toxoids-pertussis vaccine. However, subsequent studies note there is no relationship between SIDS and any vaccines.

SIDS Trends

In 1994, the National Institute of Child Health and Human Development and the U.S. National Institute of Health spearheaded the “Back to Sleep” initiative to educate parents about SIDS and its risk factors. The campaign was based on a 1992 recommendation from the American Academy of Pediatrics (AAP), which stated infants were safest while sleeping on their back or side. This recommendation was later updated to state that only the back position was safe. Today, the same program operates under the name “Safe to Sleep.”

In 1992, 120 infants died from SIDS per 100,000 live births. From 1992 to 2001, SIDS deaths in the U.S. decreased by 53 percent. This number remained constant for several years, and then further declines were reported between 2009 and 2013. As of 2017, the number of SIDS deaths per 100,000 live births has fallen below 40. Some studies suggest the decrease in SIDS cases is related to the growing number of parents who place their infants in the back sleeping position.

However, SIDS remains the leading cause of death for infants between the ages of 28 days and one year. Furthermore, some statistical studies have found disparities between different racial and ethnic groups. In surveys of mothers with varying racial and ethnic backgrounds, researchers have noted certain trends regarding co-sleeping with infants, placing infants on their backs for sleep, and the use of soft bedding in cribs. Socioeconomic factors may also be at play, as low-income families with more than one small child may resort to crib-sharing or bed-sharing in order to save space.

Boys are slightly more likely to die of SIDS than infant girls. Historically, it was believed infants were at higher risk of SIDS during colder times of the year, but more recent statistics show SIDS deaths are distributed more evenly between hotter and colder months.

How Can Parents Reduce the Risk of SIDS?

While much is still unknown about the cause of SIDS, today’s experts advise parents to take the following measures in order to reduce their child’s risk of SIDS.

  • Always place your infant in the supine (back) position for sleep. This applies to both daytime naps and nightly sleeping. That said, prone (stomach) positioning is considered relatively safe if the infant is awake, alert, and supervised, for example, when doing tummy time.
  • Avoid smoking during pregnancy and do not expose your infant to cigarette smoke.
  • Do not drink alcohol or use illegal drugs at any point of your pregnancy.
  • Share the bedroom with your infant sleeping in a crib or bassinet for a minimum of 6 months and up to a year, rather than sharing a bed with them.
  • Breastfeed your child, if possible. Remove soft bedding from your mattress before breastfeeding in bed, and avoid breastfeeding on upright sofas and chairs.

Furthermore, the U.S. Consumer Product Safety Commission (CPSC) offers the following SIDS prevention guidelines for cribs and bassinets:

  • According to the most recent reports, the safest surfaces for infants are flat and rigid with inclines of 10 degrees or less. Soft surfaces increase the risk of SIDS.
  • Never place pillows, quilts, or soft bedding in the baby’s crib or bassinet.
  • Measure gaps between the mattress and crib to ensure they do not measure more than two fingers thick.
  • When assembling the crib or bassinet, follow instructions carefully and make sure each step is completed. Contact the manufacturer if you have leftover parts, a part is missing, or if you encounter any other problems during the setup process – and do not let the infant sleep in the crib or bassinet until the issues have been resolved.
  • Never use modified cribs or bassinets, or models that are older than 10 years.
  • Do not place the crib or bassinet near windows with blinds or curtain cords, as these can be strangulation hazards. Also, be mindful of baby monitor cords.
  • Additionally, follow proper instructions when assembling play yards and other structures for your child.



Frequently Asked Questions

When can my infant sleep on their side or stomach?

According to current guidelines, infants should continue to be placed to sleep in the supine (back) position until they reach at least one year of age. Once an infant can roll from the prone (stomach) to supine (back) position and from the supine position to the prone position without assistance, the infant should be safe to sleep in any position they prefer.

Isn’t side sleeping healthier for newborns?

There is a persistent belief among U.S. infant caregivers and nursery staff that positioning newborns on their side helps clear amniotic fluid from their airway. However, the AAP states there is no evidence the side position is more beneficial in this regard. Parents should place their baby in the supine position as soon as the child can sleep in a crib or bassinet. Skin-to-skin care is recommended from the time the mother awakes after giving birth until the infant is ready for a crib or bassinet.

If I use a baby monitor, can I place my infant’s crib/bassinet in a separate room?

Many infants who die from SIDS do so without making noise or struggling. Therefore, a baby monitor – particularly one without video surveillance – may not alert you of hazardous situations. Most experts agree sharing a room with your baby’s crib or bassinet is the safest method for at least the first 6 months of life, if not the first year.

Will drinking a little bit in the first trimester increase my infant’s risk of SIDS?

The information and data pertaining to drinking during pregnancy can be somewhat conflicting. According to the Centers for Disease Control (CDC), women should not consume alcohol at any point of their pregnancy, including the time of conception. Alcohol consumption is considered a major risk factor for SIDS.

Where can I find a safe crib or bassinet for my child?

As of 2011, crib manufacturers must adhere to specific guidelines mandated by the CPSC. Additional guidance surfaced in 2021 and 2022. You should keep in mind, however, that the mattress you choose for your child is also crucial to reducing their risk of SIDS. Refer to these crib safety mandates and the additional CPSC guidelines listed earlier in this guide when determining whether a crib or bassinet is safe for your child.

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About Our Editorial Team

Danielle Pacheco

Staff Writer

Danielle writes in-depth articles about sleep solutions and holds a psychology degree from the University of British Columbia.

Dr. Nilong Vyas



Dr. Vyas is a pediatrician and founder of Sleepless in NOLA. She specializes in helping parents establish healthy sleep habits for children.


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