Untreated acute toxoplasmosis among pregnant women can lead to serious sequelae among newborns, including
neurological impairment and blindness. In Brazil, the risk of congenital toxoplasmosis (CTox) has not been fully
evaluated. Our aim was to evaluate trends in acute toxoplasmosis prevalence from 1998-2005, the incidence of CTox
and the rate of mother-to-child transmission (MTCT). A cross-sectional study was undertaken to dentify patients
who fit the criteria for acute toxoplasmosis during pregnancy. Exposed newborns were included in a historical
cohort, with a median follow-up time of 11 months, to establish definite diagnosis of CTox. Diagnoses for acute
infection in pregnancy and CTox were based on European Research Network on Congenital Toxoplasmosis criteria.
In 41,112 pregnant women, the prevalence of acute toxoplasmosis was 4.8/1,000 women. The birth prevalence of
CTox was 0.6/1,000 newborns [95% confidence interval (CI): 0.4-0.9]. During the follow-up study, 12 additional
cases were detected, increasing the CTox rate to 0.9/1,000 newborns (95% CI: 0.6-1.3). Among the 200 newborns
exposed to Toxoplasma gondii
, there were 37 babies presenting diagnostic criteria of CTox, leading to an MTCT rate
of 18.5% (95% CI: 13.4-24.6%). The additional cases identified during follow-up reinforce the need for serological
monitoring during the first year of life, even in the absence of evidence of congenital infection at birth.