Over 35 years of research and the exact causes of SIDS remain unknown. However, recent advances in medical research show us that babies that die of SIDS may not be as healthy as we once thought. Many doctors and researchers now believe that SIDS is not a single condition that is always caused by the same medical problems, but infant death caused by several different factors, including development, anatomical and / or biochemical (for example studies that suggest an abnormality in the way a SIDS baby’s brain handles serotonin.)
The factors that we know, what SIDS is not, continues to be the same. SIDS is not caused by contagious disease or immunization. It is not the result of suffocation, regurgitation, vomiting, choking, child abuse or neglect. SIDS is a diagnosis of exclusion when the cause of death remains unexplained after a thorough investigation, including a complete autopsy, investigation of the death scene, and review of the infant’s history. Almost all SIDS death occurs without any warning or symptoms when the infant is thought to be sleeping.
Although the exact causes of SIDS remain unknown, there is mounting evidence that suggests some SIDS babies are born with a brainstem abnormality that makes them vulnerable to the known “big three” risk factors for SIDS: side or prone sleeping, face-down sleeping and bed sharing. Studies reveal these abnormalities involve a portion of the brain that is in control of breathing and waking during sleep. It’s been believed for some time that babies who die of SIDS do so because they are unable to respond correctly when carbon dioxide levels build up from time to time during their sleep. Studies have shown that exhaled air (carbon dioxide) is more likely to be trapped around the face of an infant who lies tummy down (prone), especially face down, and one who sleeps with soft bedding. Normally, re-breathing this gas would prompt a baby, or anyone else, to reposition himself or herself for better airflow. The infant develops hypoxia (low oxygen levels) and hypercarbia (high levels of carbon dioxide) and succumbs to SIDS.
References: Contemporary Pediatrics, First Candle/SIDS Alliance, National Institute of Child Health and Human Development, HC Kinney – The Brainstem and Serotonin in the SIDS