The baby Westland lowland female who has yet to be named was born weighing 1kg. She required intensive care after the delivery and help breathing.
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Staff at Bristol Zoo Garden are "cautiously optimistic" for the welfare of mother and baby.
Prof Cahill said: "Along with having my own children this is probably one of the biggest achievements of my life and something I will certainly never forget.
"I have since been back to visit Kera and the baby gorilla, it was wonderful to see them both doing so well."
Gorilla C-sections have only been performed nine other times around the world.
John Partridge, senior curator of animals at the zoo, said: "The birth of any gorilla is a rare and exciting event but the birth of a baby gorilla by caesarean section is even more unusual.
"It wasn't a decision that we took lightly - Kera was becoming quite poorly and we needed to act fast in order to give the best possible treatment to mother and baby and to avoid the possibility of losing the baby."
The infant is now being hand-reared but will not be on show for the public for now.