Define navigation bar settings. Like most childhood accidents, those associated with sledding are preventable by dressing appropriately and using common sense. Insist children wear a helmet when sledding. Many of the injuries we see are to the head.
Bicycle helmets work fine.
Children sledding should be supervised by adults. Do not sled head first. Sit facing forward. Dress in thick layers - this helps prevent frostbite and hypothermia as well as protecting skin from injuries. Sleds with runners and steering mechanisms are safer than tobaggans or disks.