Impact of primary prevention on the incidence of toxoplasmosis during pregnancy.

Until now, it was assumed that primary prevention of congenital toxoplasmosis was possible by means of specific hygienic measures. A prospective survey of pregnant women was made at a hospital in Brussels over the period 1979-1986 to assess the impact of such a prevention program. In the first study period (1979-1982), when no prophylactic measures were taught, 2986 consecutive women demonstrated a seroconversion rate of 1.43% among the nonimmunized subjects; 1.07% of the seropositive patients had high antibody levels in their first serum sample. In the second study period (1983-1986), all 3563 patients were instructed to adopt prophylactic measures. The seroconversion rate in seronegative patients and the percentage of patients with high initial antibody level were 0.95 and 1.26%, respectively. Although the percentage of seroconversion was reduced by 34% in the second study period, this difference did not attain significance. These results indicate that the impact of a primary prevention program aimed at reducing congenital toxoplasmosis is limited.