Congenital toxoplasmosis

There are two common ways for pregnant woman to "catch" toxoplasmosis (become infected with the parasite that causes the disease). First, eating raw or undercooked meat that has the parasite in it can cause toxoplasmosis. Pork, mutton (sheep), and wild game (such as deer) are meats that are commonly infected with the parasite. About half of all toxoplasmosis infections in the United States are caused by eating raw/undercooked meat. The other way common way to become infected is through coming in contact with cat feces (poop) that is infected with the parasite. This happens most frequently by cleaning a litter box or by coming in contact with dirt that a cat pooped in (for example, from gardening, on unwashed fruit/vegetables, or in unfiltered water).

If a mother is infected with the parasite that causes toxoplasmosis, the parasite can get into her blood. From her blood, it can get through the placenta and into the baby's blood. Once this happens, the parasite can infect the baby's organs.

Not all babies will be infected by a mother's infection. Overall, if a mother is infected during pregnancy, there is a 20-50% chance that the baby will be infected. The risk is lowest in early pregnancy (10-25%) but the effects to the baby are usually more severe if the infection happens in early pregnancy. In later pregnancy (third trimester), there is a higher risk of infection in the baby (60-90%), but the effects on the baby are usually milder.