A study on the prevalence of seropositivity to T.gondii, Rubella virus, Cytomegalovirus and Herpes simplex virus (type 1 and type 2) was carried out in pregnant women aged 15-45 years. An overall prevalence of 40.7% to T.gondii, of 90.1% to Rubella virus, of 80.8% to Cytomegalovirus, of 82.3% and of 69% to Herpes simplex virus, respectively type 1 and type 2 was found. Cytomegalovirus infection was prevalent in women from low socioeconomic background. Herpes simplex 1 infection was higher in women living in quarters of high density population, whereas antibody prevalence to Rubella virus was higher in women from high socioeconomic setting. The expected fetal risk for T.gondii, Rubella and Cytomegalovirus infections has been assessed on the basis of the yearly seroconversion rate for each pathogen in the study population and of the known transplacental transmission rates after primary and recurrent infection in pregnancy. Thus, the expected incidence of congenital T.gondii infection in this geographic area is 0.2-0.3%, of congenital Rubella infection of 0.02% and of congenital Cytomegalovirus infection of 0.3-1.15%.