Risk of Congenital Toxoplasmosis in Newborns from Mothers with Documented Infection: Experience from Two Referral Centres

During pregnancy, primary <i>Toxoplasma gondii</i> infection can cause congenital toxoplasmosis (CT). We described the newborns' outcomes from a multicentre cohort of mothers with seroconversion (SC) at different gestational ages. This retrospective observational study (from 2007 to 2018) was conducted in two Italian referral hospitals: Fondazione IRCCS Policlinico San Matteo in Pavia and Spedali Civili in Brescia. In total, 247 pregnant women were enrolled: seroconversions were enrolled: seroconversions documented as having occurred in the two months preceding pregnancy in 12 cases (4.9%; 95% CI 2.2-7.5%), and during pregnancy in 235 cases (95.1%; 95% CI 92.5-97.8%). SC is defined as the appearance of specific anti-Toxoplasma antibodies (IgM/IgG) during pregnancy in a previously seronegative woman. A total of 56 (22.5%; 95% CI 17.3-27.7%) newborns were lost to follow-up; thus, the outcome of 193 (77.5%; 95% CI 72.3-82.7%) newborns was analyzed. The overall transmission rate of <i>T. gondii</i> infection was 23.8% (95% CI 17.8-29.8%), 0% (95% CI 0.0-11.9%) among the 1st trimester SCs, 12.5% (95% CI 5.6-19.4%) among the 2nd trimester SCs, 53.8% (95% CI 41.7-66.0%) among the 3rd trimester ones. No CT were found in the group of periconceptional infection. Among the infected newborns, clinically manifest cases were 12 (26.1%; 95% CI 13.4-38.8%), including 1 case (2.2%; 95% CI 2.0-6.4%) of stillbirth and 11 symptomatic neonates (23.9%; 95% CI 11.6-36.2%). A total of 83 amniocentesis were performed (33.6%; 95% CI 27.7-39.5%), no complication was recorded and no false positive or false negative results were registered. The results are in line with the fetal risks reported in literature for <i>T. gondii</i> infection during pregnancy, even if at a lower percentage probably due to a prompt treatment.