Congenital toxoplasmosis is a rare, but potentially serious, problem during pregnancy. Toxoplasmosis is caused by a protozoal parasite that can be found in warm-blooded animals (including humans); dried cat feces, contaminated soil, or contaminated water; and raw or undercooked meat containing infective tissue cysts. Although cats play a role in the epidemiology of the disease, there is no statistical correlation between toxoplasmosis infection and cat ownership. Toxoplasmosis can be transmitted to the fetus in utero through transplacental transmission. Both the incidence of placental transmission and severity of congenital disease depend on gestational age at which maternal seroconversion occurs. Although transmission rates from mother to fetus tend to be low early in pregnancy, fetal disease severity is highest when the fetus is infected early in gestation. Serological tests to determine maternal seroconversion are available, but their use can pose ethical and practical dilemmas. Universal maternal screening is not currently warranted in the United States because disease prevalence is low.