How Do You Look After A Pregnant Gorilla?

I would suggest calling a zoo... Where do you live that you can keep a gorilla? Why would you want to keep such an endangered animal? Other than that... I would think it would be similar to a human. Good nutrition, plenty of comfort and nature should do the rest. I would look into finding a good veterinarian to act as "midwife" and you might want to get ultrasound so that you know that the baby is positioned right and is in good health.