Prenatal diagnosis of congenital toxoplasmosis: comparative value of fetal blood and amniotic fluid using serological techniques and cultures.

The prenatal diagnosis of congenital toxoplasmosis is mainly based on biological tests performed on fetal blood and amniotic fluid. We studied the performance of neonatal diagnosis procedures and the results of fetal blood and amniotic fluid analysis. Of 127 women who contracted toxoplasmosis and underwent prenatal diagnosis, the postnatal serological follow-up was long enough to definitively diagnose congenital toxoplasmosis in 19 cases and to exclude it in 27 cases. Prenatal diagnosis allowed the detection of 94.7 per cent (18/19) of the infected fetuses. The sensitivities of tests in amniotic fluid and fetal blood were equivalent, 88.2 per cent (15/17) and 87.5 per cent (14/16), respectively. In fetal blood, biological techniques were positive in 12/16 cases and in 2/16 cases, serological tests were the only positive sign. The specificities of tests in amniotic fluid and fetal blood were respectively 100 per cent (23/23) and 86.3 per cent (19/22) (three false-positive serological results). These results, added to the lower morbidity of amniocentesis compared with cordocentesis, might lead to cordocentesis being abandoned in the prenatal diagnosis of congenital toxoplasmosis.