Does a cat have to go to the vet when she’s in labor?

Not necessarily. A lot of cats can have kittens at home without complication, but every once in a while, just like with people, there can be complications with labor if a kitten gets stuck, she's too tired, or a million other things could come into play that where there may need to be veterinary intervention, potentially a C-section to make sure that the kittens come out okay and mom makes it through.