US Pharm. 2022;47(10):32-33.

Sudden infant death syndrome (SIDS), also called crib or cot death, is the major cause of mortality in infants aged between 1 month and 1 year in the United States.1 Since the 1990s, however, new studies in pathology and epidemiology have provided the basis for understanding SIDS. The factors to reduce the risk of SIDS are briefly discussed in this article.

SIDS is generally defined as the sudden death of an infant younger than age 1 year that remains unexplained after an accurate case investigation, including a complete autopsy, examination of the death scene, and review of the clinical history.2,3 In addition, due to potential inconsistencies in the diagnosis of SIDS, the term sudden unexpected infant death (SUID) is also used to describe all unexpected infant deaths.

In the U.S., the incidence of SIDS has declined by more than 50% since the mid-1980s; the greatest reduction occurred after 1992, when the American Academy of Pediatrics (AAP) issued a recommendation to reduce the risk of SIDS by placing infants in a supine position for sleep.4 Between 1992 and 2001, the SIDS rate in the U.S. fell from 1.2 to 0.56 per 1,000 live births, while the proportion of infants sleeping in the supine position increased from 13% to 72%.5

The rate of SIDS peaks between ages 2 and 4 months, and 90% of cases occur before age 6 months. Approximately 12% of SUIDs occur during the neonatal period and 4% during the first week of the neonate’s life.1

Risk Factors

A number of risk factors for SIDS have been identified in observational and case-control studies. Those that are consistently identified as independent risk factors include:

 Maternal Factors: Young maternal age (younger than 20 years), maternal smoking during pregnancy, and late or no prenatal care.

 Infant and Environmental Factors: Preterm birth and/or low birth weight, prone sleeping positions, sleeping on soft surfaces such as loose blankets and pillows, bed-sharing, overheated rooms, and history of apnea.1,6

More than 95% of SIDS cases are associated with one or more risk factors, and in many cases, the risk factors are modifiable (sleeping position, sleep environment, or parental smoking).7

Safeguarding Factors

The following factors are protective to some extent against SIDS1:

 Breastfeeding: Breastfeeding seems to have an independent protective effect against SIDS.8 Breastfeeding for at least 2 months nearly halved the risk for SIDS, after controlling for potential confounders, such as sleep position, bed-sharing, smoke exposure, and sociodemographic factors.9 Protection increases with greater breastfeeding duration. In a separate study of more than 3 million births in the U.S., any length of breastfeeding was associated with a 15% reduction in SIDS.

Room-Sharing: Room-sharing, without bed-sharing, between parents and infants appears to reduce the risk of SIDS.10 In a case study from New Zealand in which 393 infants who died from SIDS were compared with 1,592 controls, the relative risk associated with sleeping in the prone position was reduced by approximately 80% if the infant slept in the same room as an adult.11

Pacifier Use: Use of a pacifier during sleep appears to reduce the risk of SIDS. The mechanism for this association is unclear; studies conflict as to whether there is a lowered arousal threshold during pacifier use. Because of this apparent reduction in risk, the AAP suggests offering a pacifier during sleep, provided that it does not interfere with establishment of breastfeeding.5

 Fan Use: In a population-based, case-controlled study performed in California, use of a fan was associated with a 72% reduction in SIDS risk.12 The effect was greater for infants with other environmental SIDS risk factors, including prone or side sleeping, bed-sharing, and warmer room temperature. The study was limited by low participation rates and needs confirmation by other studies.

Immunizations: SIDS is not associated with diphtheria-tetanus-pertussis vaccine or other vaccines.13 In fact, immunization may lower the risk of SIDS.1


A triple-risk representation for SIDS has been proposed, suggesting that SIDS occurs in infants with genetic factors and brainstem abnormality who experience a trigger event such as airflow obstruction, maternal smoking, or infection at a vulnerable developmental stage of the central nervous or immune system.14

Brain Abnormalities: Recent evidence suggests that a brainstem abnormality is a major contributor to the pathogenesis of SIDS. This hypothesis is suggested by the maternal and antenatal risk factors and minuscule abnormalities in the regulation of cardiac, respiratory, and sleep arousal patterns.15 Irregularities in serotonin (5-hydroxytryptamine [5-HT]) signaling in the brain have been named as a mechanism.1

Genetic Factors: The role that genetic factors play in predisposition to SIDS is not clear, but the identification of gene polymorphisms in SIDS victims suggests that specific genetic polymorphisms may interact with specific environmental risk factors to increase the susceptibility to SIDS in critical situations.16

Developmental Timing: SIDS usually happens between the second and fourth months of life, a period of important developmental changes in cardiac, ventilatory, and sleep-wake patterns in otherwise normal infants. This coincidence of timing suggests that infants are vulnerable to sudden death during a critical period of autonomic development.17

Parents and caregivers of infants should be advised how to minimize SIDS risk, especially regarding safe sleeping positions and environment.18,19

AAP Recommendations for Prevention

The following recommendations are made by the AAP.1,2,5 The recommendations apply to infants aged up to 1 year. The data underlying these recommendations are primarily based on case-control studies.
• Mothers should avoid use of tobacco, alcohol, and illicit drugs during pregnancy and after birth.
• Pregnant women should receive regular prenatal care.
• Clinicians should give anticipating guidance to all caregivers of young infants. It is worth mentioning that receipt of such counseling appears to be inconsistent, especially for aspects other than the supine sleep position, and unsafe sleep practices remain common.20
• All infants, including those with a history of prematurity, should be placed to sleep on their backs (supine) for every sleep, even if they are able to roll from their backs to the prone position. Side sleeping is not recommended.
• The recommendation for supine position sleeping also applies to infants with gastroesophageal reflux because normal infants effectively protect their airway after an episode of reflux.19
• Sitting devices (e.g., car seats, infant carriers, strollers, and swings) should not be used for routine sleep.
• If swaddling is used, it should be discontinued as soon as the infant is old enough to attempt to roll over. It is particularly important to avoid nonsupine sleep for swaddled infants.21
• Infants should be placed supine for sleep throughout the first year of life. After age 6 months, the risk of SIDS decreases substantially but is not eliminated. Once the infant can roll from supine to prone (on their stomachs) and from prone to supine, the infant can be allowed to remain in the assumed sleep position; however, when infants first start to roll over, there is a concern that those who roll prone may not be able to roll back, particularly if there is soft bedding present.22 Therefore, it remains important to avoid having soft or loose bedding in the infant’s sleep environment to prevent suffocation or entrapment if the infant rolls. For the same reason, the parent should not use bedding, pillows, or devices to try to keep the infant in a particular sleep position.
• The use of home cardiorespiratory (CR) monitors is not an effective strategy for reducing the risk of SIDS. CR monitors have high rates of false alarms and do not appear to reduce the incidence of SIDS.


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