
The disease you are talking about is toxoplasmosis.  It is a protozoan that 
lives and multiplies within cells.  In cats, the protozoan multiplies in the
intestinal cells and eggs are shed in the cat's feces.  The protozoa can
cross the placenta to infect the fetus.  The disease may be asymptomatic
after the baby is born, or it may be very severe.  Toxo may cause blindness
and mental retardation.

Having a cat in the same apartment should not be a problem; however, pregnant
women should not scoop or change the cat's litterbox.  In addition, whoever
does empty the litterbox should thoroughly wash his/her hands before handling
anything else, especially food.

Information came from _The Merck Manual, 15th Ed._

I hope this information is helpful to you.