Usefulness of quantitative polymerase chain reaction in amniotic fluid as early prognostic marker of fetal infection with Toxoplasma gondii

Objective Our purpose was to evaluate Toxoplasma gondii concentration in amniotic fluid (AF) samples as a prognostic marker of congenital toxoplasmosis. Study design A retrospective study was carried out in 88 consecutive AF samples from 86 pregnant women, which were found positive by prospective polymerase chain reaction (PCR) testing. Parasite AF concentrations were estimated by real-time quantitative PCR and analyzed in relation to the clinical outcome of infected fetuses during pregnancy and at birth, taking into account the gestational age at maternal infection. Results A significant negative linear regression was observed between gestational age at maternal infection and T gondii DNA loads in AF. After adjusting for time at maternal seroconversion by multivariate analysis, higher parasite concentrations were significantly associated with a severe outcome of congenital infection (odds ratio [OR] = 15.38/log (parasites/mL AF) [95% CI = 2.45-97.7]). Conclusion PCR quantification of T gondii in AF can be highly contributive for early prognosis of congenital toxoplasmosis. Maternal infections acquired before 20 weeks with a parasite load greater than 100/mL of AF have the highest risk of severe fetal outcome.