Clean the cat litter pan by removing the soiled litter and pouring in 1/2 inch vinegar. Let it stand for ten minutes or so, then pour out and dry. To control odors before filling again, sprinkle 1/2 cup baking soda over the bottom of the pan.
Some people have environmental and health concerns about the type of cat litter available commercially. Pregnant women especially are at risk for a virus called toxoplasmosis, which can be contracted by handling cat litter, the litter box, or the box liner. Try to keep your cat's litter box area clean at all times to reduce the risk, but pregnant women should avoid handling anything to do with cat litter for the duration of their pregnancy.
If you're really ambitious, you can make your own natural cat litter. Just mix a small box of baking soda with two to three inches of dry, sandy clay soil.