How old does a cat have to be in order to be pregnant?

Cats can get pregnant as early as six months. It's not good for them to reproduce early.

Likewise, male cats can be viable early. Both sexes are prone to mature early when they suffered deprivation as kittens.

Don't dawdle about getting any cat neutered or spayed because of their age. Thinking the cat will be fixed before kittens arrive is how we have so many kittens without homes.