Diagnosis of Toxoplasma infection in the pregnant woman and the unborn child: current problems.

Prevention of congenital toxoplasmosis requires identification of non immune women at the beginning of pregnancy, instruction on how to avoid contamination and a serological follow-up of the women until the delivery. The latter is easily achieved by a repeated testing for specific IgG and IgM. Most of the interpretation difficulties arise from results suggestive of recent infection obtained on a first specimen. If no rise in IgG titer is demonstrated on a second serum sample, the use of additional tests studying other Ig-isotypes or acute-phase IgG antibodies can be helpful, mainly as a way to exclude the possibility of infection acquired during pregnancy. Congenital infection can be investigated by biological measurements on fetal blood and by ultrasound examination. Detection of specific IgM and IgA in fetal serum must be interpreted with care because of the existing risk of contamination with maternal blood. Demonstration of Toxoplasma gondii in fetal blood or amniotic fluid by mouse inoculation definitely proves the diagnosis; though less sensitive, tissue culture offers the advantage of a more rapid result. The very promising results obtained by the PCR-method applied to amniotic fluid samples give the hope that it can replace som of the existing confirmatory methods.