Serodiagnostic methods were evaluated in prenatal screening for primary Toxoplasma infections acquired during pregnancy in the Helsinki area. Altogether 44,181 sera were obtained consecutively during each trimester from 16,733 mothers. All IgG-containing samples were first examined by a sensitive mu-capture (IgM) ELISA, and positive results were reassessed by IgM immunoblotting and indirect IgM ELISA. An assay measuring the avidity of toxoplasma IgG was used for the first time under screening conditions. Patients suspected to have recent toxoplasmosis were reexamined by IgA ELISA and selectively by the differential agglutination assay (HS/AC test) and IgE ELISA; 16 women with diagnostic increases in IgG titer, 36 with IgM fulfilling strict specificity criteria, and 25 with IgG of low avidity were identified. The measurement of IgG avidity was a highly specific and sensitive method suitable for verification of acute primary Toxoplasma infections during pregnancy.

The cause of stillbirth and preterm delivery is often unknown. We studied the prevalence of Chlamydia trachomatis antibodies in mothers with stillbirth and preterm labor. Serum specimens from 72 mothers with stillbirth after the 21st gestational week, and from 48 mothers with preterm delivery between gestational weeks 23 and 29, both from the greater Helsinki area, and cord blood from 96 consecutive liveborn deliveries at the Department of Obstetrics and Gynecology, the University of Helsinki, were studied for antibodies to C. trachomatis immunotypes CJHI, GFK and BED by microimmunofluorescence test. The prevalence of C. trachomatis antibodies was highest, 33.3%, in mothers with stillbirth, 18.8% in mothers with preterm delivery, and 10.4% in cord blood. The IgM seropositivity rate was high among mothers with preterm delivery (8.3%). We conclude that C. trachomatis IgG antibodies are frequently detected in sera from mothers with stillbirth, suggesting past infection, while mothers with preterm delivery often have serum IgM antibodies, suggesting of acute infection.

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Social environment seems to be the most powerful factor, predicting both IgG seroprevalence and recurrences during pregnancy.

Congenital toxoplasmosis is a risk for fetus both in 'low' and 'high risk' areas. A cost-benefit analysis based on data from a Finnish prospective study (20.3% seropositivity of pregnant mothers and incidence of 2.4/1,000 seronegative pregnancies) and on Finnish cost data was performed to compare the no-screening and screening alternatives for primary toxoplasma infections during pregnancy. A maternal-feto transmission risk of 40%, effectiveness of treatment of 50%, and discount rate of 4% were used as other baseline probabilities. The calculations were carried out by decision analysis combined with sensitivity analysis. The total annual costs of congenital toxoplasmosis without screening amount to US$ 128/pregnancy/year, and with systematic serological screening, US$ 95/pregnancy. Thus screening reduces the costs by 25%. The present value of net savings in Finland would be US$ 2.1 million every year. A one-way sensitivity analysis showed that screening together with health education is preferable to health education without screening if the incidence of maternal primary infections exceeds 1.1/1,000 and effectiveness of treatment is better than 22.1%. Screening for toxoplasma infections during pregnancy is economically worthwhile even in a country with a low incidence. A scheme of systematic screening for maternal primary toxoplasma infections combined with health education should be considered.