Serological survey for congenital toxoplasmosis among 4,136 pregnant women.

A prospective seroepidemiological survey for latent congenital toxoplasmosis was carried out among 4,136 women and 3,787 of their offspring in and around Montreal. The indirect immunofluorescent antibody test was used to titrate specific IgG and IgM antibodies and results were standardized in international units. The prevalence of antibodies was 40-8% for the mothers and 36-4% for the babies. Mean annual seroconversion rate was 0-95%. Thus, 30 women would have been expected to acquire toxoplasmosis during pregnancy: two cases only were observed and the reasons for it are discussed. Four cases of congenital toxoplasmosis were diagnosed serologically (0-1%), none of them showed any signs of illness. Preventive treatment was administered to 12 of 52 pregnant women suspected of a recently acquired infection.