Sudden Unexpected Infant Death (SUID)
Sudden Unexpected Infant Death (SUID) is all-encompassing term that includes unexpected death of explained or unexplained etiology that occurs during infancy (from birth to one year of age). Sudden Infant Death Syndrome (SIDS) is one subcategory of SUID. Other causes of SUID include suffocation, strangulation, entrapment, infection, ingestions, metabolic disease, and trauma .
The Sudden Infant Death Syndrome (SIDS) definition:
the sudden death of an infant under twelve months old, which remains unexplained after a thorough case investigation including performance of an autopsy, examination of the death scene and review of clinical history .
In the United States, the rate of SIDS has decreased by >50% since 1994 when the “Back to Sleep” campaign was introduced. In 2017, there were 3,600 cases of SUID, of which 1,400 were classified as SIDS. This corresponds to a decline in the rate of SIDS from 1.2 deaths per 100,000 live births in 1992 to 0.35 deaths per 100,000 in 2017. In part this is because SUID is less often classified as SIDS and more often as accidental asphyxiation or other causes . Despite the significant improvement, SIDS remains the most common cause of death in infants one month to one year of age .
Trends in Sudden Unexpected Infant Death by Cause 1990-2017
Researchers use the Triple-Risk-Model to understand SIDS.
- Vulnerable infants have underlying abnormalities that cause dysfunction in cardiorespiratory and/or arousal systems. Premature infants, infants with low birth weight, twins, and infants with a sibling that died from SIDS are also at higher risk [1,4].
- Critical developmental period occurs during the first 6 months of life when there is rapid growth and changes in homeostatic patterns. 90% of infants who die from SIDS are <6 months old .
- Outside stressors include prone and side sleeping and other sleep environment factors (soft bedding, overheating, co-sleeping), maternal smoking during pregnancy, and secondhand smoke exposure .
The risk of SIDS is higher in male infants at a ratio of approximately 3:2 . There are significant racial disparities with the highest incidence of SIDS in African Americans and American Indian/Alaska Natives. Other risk factors include lack of prenatal care and young maternal age .
"Back to Sleep" Campaign
"Back to Sleep" (now known as "Safe to Sleep") is a campaign initiated in 1994 by the National Institute of Child Health and Human Development in response to recommendations made by the American Academy of Pediatrics. After its introduction, the rate of SIDS fell dramatically with a simultaneous increase in the percentage of infants sleeping in the supine position .
The underlying cause of SIDS remains undetermined, with a multifactorial underlying etiology. Apnea once formed the prevailing hypothesis regarding the cause of SIDS; however studies demonstrating infants succumbing to SIDS experienced fewer apneic events compared to infants surviving to childhood weakened support for this hypothesis .
Currently, brainstem deficits leading to a diminished response to hypercarbia, hypoxia and hypothermia is considered one of the leading hypotheses regarding the underlying etiology of SIDS .
Evidence of ethnic disparities in SIDS rates led to the investigation of various underlying genetic causes. Current research focuses on genetic abnormalities of the serotonergic system, including the serotonin transporter gene SLC6A4 or 5-HTT. Other genetic investigations focus on the autonomic nervous system, nicotine-metabolizing enzymes, ion channel proteins, inflammatory regulators, energy production, hypoglycemia, and thermal regulation .
SIDS remains, by definition, a diagnosis of exclusion.
However, certain features at autopsy are consistent with SIDS, including:
- Encephalomegaly, pulmonary edema, intrathoracic petechiae, microcardia, reduced kidney size, unclotted blood in the heart, and an empty bladder and rectum and findings consistent with chronic hypoxia .
Following the success of the "Back to Sleep" campaign, the American Academy of Pediatrics issued a policy statement in 2011 highlighting methods to reduce the incidence of SIDS .
The recommendations consist of the following:
Supine sleep position: Infants should be placed in the supine position by the caregiver for every sleep until reaching one year of life. The supine position is not associated with an increased risk of aspiration, and is still recommended in infants with gastroesophageal reflux. Side sleeping similarly carries an increased risk of SIDS and is not recommended.
Use of a firm sleep surface: The AAP recommends use of a firm crib mattress covered by a fitted sheet. The mattress should extend to the side of the crib without gaps. Pillows and other soft materials such as quilts, comforters or cushions should not replace a mattress, or be used on top of a mattress, even when covered in a fitted sheet. Infants should not be placed in beds due to the risk of suffocation. Other hazards, such as dangling cords or electrical wires, should be cleared from the area. Other safety devices, such as strollers, slings, car seats or carriers should not be used for routine sleep, due to the lack of a stable surface.
Room sharing without bed sharing: Avoidance of sleep in an adult bed reduces the risk of accidental suffocation or entrapment. Sleeping in a crib in the same room as the caregiver facilitates feeding, comforting and monitoring of the infant. There are no recommended measures to make bed sharing safe. Twins require separate sleeping areas and should not co-sleep in the same crib.
Crib objects: The crib should remain clear of soft objects and loose bedding, such as pillows, toys, or comforters.
Prenatal care: Regular prenatal care is recommended due to an association with a decreased risk of SIDS.
Smoke and other drug exposures: Avoidance of smoke exposure is recommended both during pregnancy and after birth due to a decreased risk of SIDS. Similarly, avoidance of alcohol and illicit drugs during and after pregnancy is recommended.
Breastfeeding: Breastfeeding is associated with a lower risk of SIDS. While fully breastfed infants experience the greatest protective effect, partially breast fed infants are also at lower risk of SIDS.
Pacifier use at nap and bedtime: The use of pacifiers appears to provide a protective effect against SIDS. The protective effect appears to continue even after a pacifier falls out from the infant’s mouth, and need not be reinserted during sleep. The pacifier should not be hung around the infant’s neck or attached to other objects that could pose a risk of strangulation.
Overheating: Studies demonstrate an increased risk of SIDS with overheating, thus infants should be assessed for signs of overheating such as sweating or feeling hot to the touch. There is currently insufficient evidence to suggest a benefit to use of a fan in reducing the risk of SIDS.
Tummy time: Supervised, awake time spent in the prone position aids in prevention of positional skull deformities and promotes development of upper body muscles.
Additional measures: The AAP guidelines also suggested the avoidance of commercial products marketed to prevent SIDS, as there is insufficient evidence to show these items provide a protective effect against SIDS. The use of home cardiorespiratory monitors to prevent SIDS is similarly lacking in evidence to demonstrate a protective effect. Health care professionals should promote SIDS risk-reduction recommendations. Media and manufactures should follow safe-sleeping guidelines in their marketing of products. The guidelines promote expansion of the national campaign for SIDS prevention and continued research into reducing the risk of SIDS.
Management of Sudden Infant Death
- There are few things more devastating to a family than the sudden unexpected death of an infant. It is important for the pediatrician to be in contact with the family soon after the event to obtain a thorough history and permission for an autopsy. It is imperative that the death scene is investigated. Avoid accusations.
- As soon as the autopsy results are known, the parents must be informed of the findings
- 4-6 weeks after the death, the parents should visit the pediatrician to discuss any questions that the family may have.
- The parents and family can be directed to organizations that are available for parents of SIDS victims. Not all parents are interested in joining groups, so do not force this upon them. The link below is to one such type of support organization.
- If the mother becomes pregnant again, make yourself available for questions. In addition, after the birth of the next child, be prepared for the mother to be very anxious until the high incidence periods of SIDS has passed or until the new infant live past the time the previous child died. The family may request a monitor, sleep/apnea studies, refuse immunizations, and call often. Be patient.
Moon RY et al. SIDS and Other Sleep-Related Infant Deaths: Evidence Base for 2016 Updated Recommendations for a Safe Infant Sleeping Environment. Pediatrics in Review 2016; 138 (5) e20162940; DOI: 10.1542/peds.2016-2940
Centers for Disease Control and Prevention. Sudden Unexpected Infant Death and Sudden Infant Death Syndrome. Accessed March 13, 2020. https://www.cdc.gov/sids/data.htm
Corwin M.J. Sudden infant death syndrome: Risk factors and risk reduction strategies. In AG Hoppin (Ed.), UpToDate. Updated February 3, 2020. https://www.uptodate.com
- Willinger M et al. Defining the sudden infant death syndrome (SIDS): Deliberations of an expert panel convened by the National Institute of Child Health and Human Development. Pediatr Pathol 11:677-684, 1991
- Moon RY et al. Sudden Infant Death Syndrome: An Update. Pediatrics in Review 2012;33;314 DOI: 10.1542/pir.33-7-314
- Schechtman VL et al. Sleep apnea in infants who succumb to the sudden infant death syndrome. Pediatrics 87:841-846, 1991
- Rand CM et al. Congenital central hypoventilation syndrome and sudden infant death syndrome: disorders of autonomic regulation. Semin Pediatr Neurol. 2013 Mar;20(1):44-55. doi: 10.1016/j.spen.2013.01.005.
- Task Force on Sudden Infant Death Syndrome. Policy Statement: SIDS and Other Sleep-Related Infant Deaths: Expansion of Recommendations for a Safe Infant Sleeping Environment. Pediatrics 2011; 128:5 1030-1039; published ahead of print October 17, 2011, doi:10.1542/peds.2011-2284