In the immunocompetent host, toxoplasmosis is classified as congenital, acquired, or ocular. The most common finding is lymphadenopathy. If the mother was infected prior to the current pregnancy, virtually no risk of fetal transmission exists. If the mother becomes infected during pregnancy, the fetus is at risk regardless of whether the mother is symptomatic. Fetal infection with T gondii may result in stillbirth or abortion.
Congenital infection is most severe if acquired in the first or, in some cases, second trimester.
Infection during the second or third trimesters tends to be asymptomatic. Seventy-five percent of infants born with congenital toxoplasmosis infection are asymptomatic. Eight percent show severe CNS impairment, which might not manifest for several years. In the immunocompetent host, infection with T gondii may be indistinguishable from infectious mononucleosis. Focal, necrotizing retinitis is the characteristic lesion.