The most common cause of unintentional deaths in children is Motor vehicle accidents
“Unintentional injuries account for 40% of childhood deaths. Motor vehicle accidents are the most frequent cause of these deaths (58.2% of unintentional deaths). The proper use of child restraints is the most effective way to prevent injury or death, and the American Academy of Family Physicians and the American Academy of Pediatrics strongly recommend that physicians actively promote the proper use of motor vehicle restraints for all patients. Drowning accounts for 10.9% of all unintentional deaths in children, poisoning for 7.7%, fires 5.7%, and falls 1.4%.” ABFM
Reference
Prevention of unintentional childhood injury. Am Fam Physician 2013;87(7):502-509.