Shaken baby syndrome (SBS) is a triad of medical symptoms: subdural hematoma, retinal hemorrhage, and brain swelling from which doctors, consistent with current medical understanding, infer child abuse caused by intentional shaking. In a majority of cases there is no visible sign of external trauma.

SBS is often fatal and can cause severe brain damage, resulting in lifelong disability. Estimated death rates (mortality) among infants with SBS range from 15% to 38%; the median is 20%–25%. Up to half of deaths related to child abuse are reportedly due to shaken baby syndrome.^{[not in citation given]} Nonfatal consequences of SBS include varying degrees of visual impairment (including blindness), motor impairment (e.g. cerebral palsy) and cognitive impairments.^{[citation needed]}

The characteristic injuries associated with SBS include retinal hemorrhages, multiple fractures of the long bones, and subdural hematomas (bleeding in the brain). These signs have evolved through the years as the accepted and recognized signs of child abuse and the shaken baby syndrome. Medical professionals strongly suspect shaking as the cause of injuries when a baby or small child presents with retinal hemorrhage, fractures, soft tissue injuries or subdural hematoma, that cannot be explained by accidental trauma or other medical conditions. About three quarters of cases involve retinal hemorrhaging. Additional effects of SBS are diffuse axonal injury, oxygen deprivation and swelling of the brain, which can raise intracranial pressure and damage delicate brain tissue. A recent study found the prevalence of retinal hemorrhages in abusive head trauma was 78%, but only 5.3% in nonabusive pediatric head trauma. Victims of SBS may display irritability, failure to thrive, alterations in eating patterns, lethargy, vomiting, seizures, bulging or tense fontanels (the soft spots on an infant's head), increased size of the head, altered breathing, and dilated pupils.