ABSTRACT
OBJECTIVE: To determine the incidence of primary toxoplasma infection in women of childbearing age. DESIGN: A retrospective study of seroconversion on stored pairs of sera taken for routine antenatal testing. SETTING: The antenatal clinics and general practices of Sheffield between July 1989 and October 1992. SUBJECTS: One thousand six hundred and twenty-one women on whom pairs of sera, separated by more than 500 days, had been received. MAIN OUTCOME MEASURE: Rate of primary infection determined by seroconversion as measured by the presence of antibody in the second serum and its absence in the first. RESULTS: Of 1621 women, 160 (9.9%) were initially seropositive. One seroconversion was detected in 2966 woman years of observation for susceptibles. The projected rate for primary infections was 0.23 (95% CI 0.0059-1.3) per 1000 pregnancies. CONCLUSIONS: The rate is much lower than for earlier estimates of incidence in the UK but agrees with a more recent estimate from Sheffield and suggests a falling incidence.
