It is a good idea to take extra precautions when you are pregnant. Cats can transmit a parasite known as Toxoplasmosis to people. This parasite rarely causes problems in healthy adults but can be devastating to a developing fetus. To reduce exposure, pregnant women should not clean litter boxes; someone else should remove the feces from the litter box within 24 hours. Pregnant women should also wear gloves while working in the garden.
For more information, please see the story Are Cats Dangerous to Pregnant Women?