If a child is born deaf and blind are they sentenced to go to hell?

I mean they can't hear or even read Jesus' gospel so how can they be saved? When Jesus said his message was for all mankind how did he make it true also for deaf and blind kids? They may have mental capability to understand his message but how do you communicate this to such a person? Why would God put such a person into the world if he knew they were condemned to eternal damnation in the after-life?