[Risk assessment of vertical transmission of Toxoplasma infections]

It is important to estimate the risk of congenital toxoplasmosis infection and its clinical sequelae. This information will assist the clinical counselling of pregnant women with acute toxoplasmosis and may guide individual decisions on investigative and therapeutic options.

Since January 1998 to July 2000 we collected data on 63 pregnant women referred to our Prenatal Diagnosis Centre for suspicion of acute maternal toxoplasmosis. In case of positive screening tests for IgG and IgM or documented seroconversion, we sent samples of maternal serum to a reference laboratory to detect specific IgM, IgG, IgA antibodies and IgG avidity. We estimated the risk of mother-to-child transmission as high or low in relation to gestational age at the time of maternal seroconversion. Antiparasitic treatment with spiramycin since before confirmation of infection and evaluation of fetal biometry were done. In high risk women we advised amniocentesis for polymerase chain reaction (PCR). If infection was diagnosed in the fetus, the regimen of treatment was changed. Live-born children of all these mothers were followed up serologically for at least 1 year.

In 13/63 cases (20%) we excluded maternal infection. Thirty-six out of 63 cases (57%) with high transmission risk underwent an amniocentesis, except one case requesting termination of pregnancy. Four out of the remaining 14 cases estimated at low risk had an amniocentesis for maternal anxiety. Among high risk women, PCR on amniotic fluid was positive in 4 cases (10%): 2 of these requested pregnancy termination, while the other 2 decided to proceed with the pregnancy and the therapy was shifted to 3 weeks courses of pyrimethamine and sulphadiazine with folinic acid alternating with spiramycin. Five infants were lost at follow-up, 20 babies resulted not infected and the remaining 21 are still followed-up.

It is possible to select by specific serological tests, high risk cases for mother-to-child transmission of infection and to decide a specific approach.