Infants potentially at risk for congenital toxoplasmosis: a prospective study.

Fifty-two children were selected as being potentially at risk for congenital toxoplasmosis by serologic testing of 8,043 pregnant women in the Oslo area. These infants were then studied during the neonatal period and subsequently followed up for three years. Three were found to be congenitally infected with Toxoplasma gondii, and one infant was dysmature at birth. The diagnosis was confirmed by persistent dye-test antibodies and by recovery of parasites in placenta and/or amniotic fluid. The Toxoplasma indirect fluorescent IgM-antibody test remained negative, while measurements of cord IgM and IgA levels and serial estimations of specific antibody load supported an early diagnosis. The specific cell-mediated immunity, as measured by the in vitro lymphocyte stimulation test, turned positive at 1 year of age and then increased markedly during the second and third years. The lymphocyte responses of the uninfected children, however, remained negative. The infected children received pyrimethamine/sulfadiazine treatment during their first year, with no clinical signs of congenital toxoplasmosis.