I have always had cats - through 3 pregnancies.
There IS a disease that can be caught from cats, though called toxoplasmosis.
We do not run as much of a risk from it in our family because our cats are completely indoor cats - they do not go out doors at all. So they do not have as big of a chance to catch this disease and pass it on.
BUT the biggest risk that anyone runs of catching this from a cat is from cleaning out the litter box. That is where it is passed, through the cat's feces. So if you have a cat, during your pregnancy - let someone else clean the litter box. There is no sense in taking the risk.
Also, you might check to see if you have developed an allergy to cats. Ask your doctor to run an allergy test. If this is the case - you might need to give the kitty away.
But otherwise you do not need to get rid of your cat, just take cleanliness precautions.