The disease you are worried about is toxoplasmosis. It can cause a lot of problems, including miscarriage.
It is very very rare for chickens to carry this, but it is possible. From what I've read, when they do have toxoplasmosis, chickens get very sick and often die. Cats, on the other hand, do not show obvious symptoms- that is why the cats pose such a problem. 
Of course you should talk to your doctor. But if you've had the chickens for a while (at least several months) without any signs of illnesses, you should be completely fine. It would be other people's cats (and new chickens) that you need to worry about, not your personal chickens if they are in good health.
-MTchick