Congenital toxoplasmosis and proposal of a new classification for the likelihood of primary maternal infection: analysis of 375 cases in Southeast Italy

Objective: The aim of this study was to propose a classification in order to stratify the probability of an acute Toxoplasma infection in pregnancy and to estimate the risk of vertical transmission. Study design: We evaluated the likelihood of a primary maternal infection according to the Lebech classification and to the modified-Lebech classification proposed for our group of 375 patients referred for a suspected primary maternal infection. Fetal diagnosis included the examination of amniotic fluid by PCR to detect Toxoplasma DNA as a confirmation test. Results: Differences between the old and new classification resulted statistically significant for old classes defined as probable and unlikely with a clear shift of cases from the unlikely to the probable class in the new classification. Transmission rate showed a significant (p <.05) increase of the transmission rate in the probable class in our new classification as compared with the Lebech one. Conclusions: Results obtained in the present study suggest that the new IgG avidity-based classification herein proposed could estimate more precisely the likelihood of a primary maternal Toxoplasma infection as well as the risk of fetal infection, when compared with the historical Lebech Classification.