According to the Centers for Disease Control and Prevention:
Sudden Infant Death Syndrome (SIDS) is defined as the sudden death of an infant less than one year of age that cannot be explained after a thorough case investigation is conducted, including a complete autopsy, examination of the death scene, and review of the clinical history.
SIDS is the leading cause of death among infants aged 1 to 12 months, and is the third leading cause overall of infant mortality in the United States. Although the overall rate of SIDS in the United States has declined by more than 50% since 1990, rates have declined less among non-Hispanic Black and American Indian/Alaska Native infants. Preventing SIDS remains an important public health priority.
Data on SIDS from National Center for Health Statistics mortality reports document the decline of SIDS as a cause of death.