What is the leading cause of death in an infants first year life?

The leading cause of death in an infant's first year of life is sudden infant death syndrome (SIDS). SIDS is the unexpected death of a child under one year of age, which remains unexplained after a thorough investigation. It is the leading cause of death in infants between one month and one year old, and although the exact cause is not known, certain risk factors have been identified, such as sleeping on the stomach, exposure to secondhand smoke, co-sleeping, overheating, and certain underlying medical conditions.