Causes of SIDS

Health care providers and other medical professionals are not completely certain about what causes SIDS, but extensive research has revealed several possibilities. Many experts believe that one risk factor alone is not enough to cause SIDS, but a combination of factors increases the risk.

Some parents worry that vaccinations given to babies during their first few months of life can cause SIDS, since this time period coincides with higher incidence of SIDS. In 2003, after extensive review, the Institute of Medicine confirmed that there was not enough evidence to prove a causal connection between vaccines and SIDS. Other studies using Vaccine Safety Datalink (VSD) and Vaccine Adverse Event Reporting System (VAERS) data also have shown no association.

SIDS Risk Factors

The medical community has determined that the following factors increase the risk for sudden infant death syndrome:

  • Stomach or side sleeping. SIDS occurs more often in babies who sleep on their stomachs. Because they can roll over to their stomachs, babies put down on their sides also are at higher risk. Some researchers believe that stomach sleeping puts pressure on the jaw, narrowing the airway and causing breathing difficulties.

    Doctors place an important emphasis on back sleeping. Since the American Academy of Pediatrics (AAP), National Institute of Child Health and Human Development (NICHD), and a number of SIDS organizations began the "Back to Sleep" educational campaign in 1994, SIDS deaths have decreased by more than 50%. [Note however, that according to research reported in 2004 by Dr. Michael Malloy of the University of Texas, Galveston and Dr. Marian MacDorman of the National Center for Health Statistics, this decrease has been offset by increasing numbers of infant deaths attributed to other causes, such as suffocation.]

  • Soft sleep surfaces and loose bedding. Waterbeds, sofas, pillows, plush toys, and blankets have all been associated with a higher incidence of SIDS and infant suffocation. Co-sleeping is a related risk factor.
  • Excessive warmth. Babies who sleep with many layers of clothing and blankets are at higher risk for SIDS, as are babies who sleep in overheated rooms. Some researchers theorize that excessive warmth causes a baby to sleep more soundly, making it more difficult to wake up.
  • Smoking during pregnancy and secondhand smoke. Infants whose mothers smoked during pregnancy are three times more likely to experience SIDS. Nicotine may affect an infant's central nervous system and oxygen levels before birth, increasing SIDS risk.

    Exposure to secondhand smoke, such as in the home or in cars, also increases the risk for SIDS. In 2006, the Centers for Disease Control and Prevention (CDC) reported that chemicals in secondhand smoke can damage the brain and impair its ability to regulate infant breathing properly. The CDC also noted that infants who die of SIDS often have higher blood levels of nicotine and cotinine (substance from exposure to secondhand smoke) than babies who die from other causes.

  • Alcohol and drug use during pregnancy. Similar to smoking, drinking alcohol and using drugs during pregnancy compromises the health of the baby and makes him or her more susceptible to SIDS.
  • Teenage births. SIDS occurs more frequently in babies born to teenage mothers than in babies born to older women.
  • Insufficient prenatal care/premature births and low birth weight. Premature and smaller babies are at higher risk for sudden infant death syndrome. It has been suggested that low socioeconomic status also may pose a risk and factors such as infant neglect, mistreatment, and abandonment may increase the risk.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 28 Aug 2008

Last Modified: 18 Nov 2011