Women who are planning on starting a family need to be aware of a parasite called toxoplasma gondii, which can cause an infection call Toxoplasmosis in humans.  Cats are one of the animals that can carry and spread this parasite to humans through infectious cysts shed in their stool.  Toxoplasmosis will generally cause mild flu-like symptoms in humans that goes away after a few days, but it can be very harmful to fetuses in teh first trimester of pregnancy. 

Although this scares many people, Toxoplasmosis is only infectious under extremely particular circumstances that almost never coexist.  A cat has to have had a recent infection, it has to be shedding the cysts which have to exist in stool in the litter box for more than 24 hours, a woman needs to get the stool in their mouth or eye, and she has to be in her first trimester.  Cats shed toxoplasma cysts in their feces three to ten days after eating infected tissues from another animal; so your cat would have had to hunt and eat an infected mouse or other creature in order to be infected himself.  The only way an indoor cat woudl be infected is if you have rodents in your house that it hunts, or if he is on a raw food diet (the parasite is transmissible to both cats and humans who consume raw meat).  Statistics show you are more likely to contract Toxoplasmosis from handling raw meat or gardening in infected soil. 

Doctors suggest letting someone else scoop the litter for you during your first trimester.  If that's not possible, they advise wearing gloves, using litter box liners, and changing the entire box every 24 hours.  Still, you'd have to get the cyst that got onto your hand into your mouth or eyes, and that can be avoided by washing your hands when you're done cleaning the litter box.

Since many people do not even realize that they have had Toxoplasmosis, you should have your doctor or midwife do a blood test for evidence of past infection before you get pregnant or as early in pregnancy as possible.  If the test is positive, you have already had the infection and do not need to worry about passing a new infection to your baby.  If the test is negative, you should take the precautions above, wear latex gloves when you handle raw meat, wear gardening gloves while doing yardwork, and wash your hands thoroughly after these activities.