The baby gorilla was born at Bristol Zoo Gardens on Dec. 15, the zoo's deputy director Dr. Bryan Carroll said.
The newborn, which has not been named, has started suckling and is doing well, the zoo's senior primate expert Mel Gage said. Its sex has yet to be determined.
It is the second baby for the 30-year-old mother, Salome, who first gave birth almost 20 years ago.
"The new baby is incredibly cute and Salome is being a very attentive mom and her father Jock is being very protective of his family troop - we couldn't have hoped for more," Gage said.
Veterinarians had diagnosed Salome with a diminished ovarian reserve, meaning she was not producing ova, Carroll said.
After consulting gynecologist David Hill, a senior lecturer at the University of Bristol, zoo veterinarians gave Salome a fertility drug called clomifene to stimulate ovulation, Carroll said.
Salome became pregnant three months after first receiving the treatments, he said.
"Female gorillas, like their human counterparts, find conceiving more difficult as they get older, so zoos may now be able to give some of their important breeders a helping hand," Caroll said. "Being able to treat female gorillas with human fertility drugs is potentially a very important breakthrough."
Carroll said the treatment was likely to be replicated worldwide.