Do you need to take your cat to the vet if she is pregnant?

No.

I assume that you're worried about the risks of toxoplasmosis, which is only a risk if you're letting your cat eat raw meat and your wife handles the cat feces directly. More people in the western world get the parasite from handling/consuming uncooked meat, so you should be more concerned about letting your wife handle the steak.

There's so much fear mongering about pets and pregnancy. Your cat is a part of the family too, I hope that you seriously weren't considering "getting rid" of a family member without doing your homework first. While parasites are fun to talk about, be more concerned about proper exercise and diet.

Read more info on toxoplasmosis at the CDC.gov website.

good luck with the new little one!