Congenital toxoplasmosis: assessment of risk to newborns in confirmed and uncertain maternal infection.

Unlabelled: We identified 205 newborns at risk of congenital infection based on their mothers' immunological status during pregnancy, using the criteria established by the European Research Network on Congenital Toxoplasmosis to define the likelihood of infection in pregnant women. Of the 205 newborns, 60 (29.2%) were born to mothers with documented seroconversion, 49 (23.9%) to mothers with probable infection, 60 (29.2%) to mothers with possible infection, and 36 (17.6%) to mothers who were unlikely to be infected. Infection was transmitted to the child in 13 out of 60 cases (21.6%) of seroconversion, in 2 out of 49 (4.1%) cases of probable infections and in none of the possible and unlikely cases. The results were further analysed considering only the 109 newborns of mothers with confirmed and probable infection; in this group, toxoplasmosis was not transmitted to any of the 45 newborns of mothers infected in the first trimester of pregnancy, whereas it was transmitted to 5 out of 29 (17.2%) cases of seroconversion and 2 out of 12 (16.6%) with probable infection in the second trimester, and to 8 out of 23 (34.8%) with confirmed infection in the third trimester (no probable infections were dated in the third trimester). Among the newborns of mothers with seroconversion, the risk of symptomatic infection was 10.4% in the second trimester and 8.7% in the third trimester.

Conclusion: the authors have quantified the risk of transmission of toxoplasmosis infection, not only in cases of seroconversion, as reported by others, but also in infections defined as probable or possible based on presence of IgM and/or IgA and with medium-high IgG levels. Probable infections in the second trimester of pregnancy carries the same risk of transmission as seroconversions and pregnant women and their newborns in these cases should undergo the same diagnostic and therapeutic approach. It is suggested that newborns of mothers with certain and probable infection must be carefully observed and undergo clinical and serological testing to identify and treat the infection as soon as possible. In the case of possible or unlikely maternal infection, serological testing at longer intervals is nevertheless advisable without the need for treatment.