Repeated serological investigations (CFT, IFT, ELISA) of 50 000 pregnant women revealed that 5.1 ‰ pregnancies in the Karviná district, Czech Republic are threatened by toxoplasmosis. In 2.8 ‰ pregnancies the infection was contracted shortly before pregnancy, one third of them ended by spontaneous abortion. In this group the birth of a congenitally infected infant is rare. Primary infections of women who are already pregnant (2.3 ‰ of pregnancies) are much more serious. This number comprises 1.2 ‰ pregnancies with a spontaneous abortion and 1.2 ‰ pregnancies leading to the delivery of a congenitally infected infant. By early detection, i.e. repeated serological examinations in all pregnancies, and by treatment of patients with Toxoplasma infections this hazard can be reduced substantially, i.e. to one eighth.

        Key words: toxoplasmosis, pregnancy, spontaneous abortion