It has happened before. It’s a complete toss up and not worth the risk.
One incident had a female matriarch care for an injured child, protect them from hostile males, and then lay them at the service door so that zoo staff and paramedics could safely retrieve the child.
Other incidents, primarily by males, have had the gorillas drag the kids around like rag-dolls or beat them to death. Even a probing “love-tap” from a fully grown silverback is usually fatal to a regular child.
Harambe was curious and checking out the child, but that could have changed in an instant for any reason. It would have taken a fraction of a second for him to kill the kid.
Not against a fully grown child. That’s usually a one sided encounter. Coughing baby vs Hydrogen bomb. Harambe stood no chance. A gorilla would be instantly mauled by a child.