OBJECTIVE To analyze the outcome of maternal primary cytomegalovirus (CMV) infection. METHODS Retrospective analysis of a cohort of 238 patients with maternal primary CMV infection detected at routine screening. The cases were managed with serial ultrasound (US) scans, and amniocentesis was performed in 36.1% of cases. All prenatal results were confirmed at birth. RESULTS The average age was 31.9 (18-44) years. Patients were symptomatic in 21% of cases. The rate of intrauterine transmission was 24.9%, and it was 8.8%, 19%, 30.6%, 34.1% and 40% in the preconceptional period, the periconceptional period, and the first, second and third trimesters of pregnancy, respectively (p = 0.025). There was a significantly higher risk of US abnormalities when maternal infection occurred during the preconceptional or periconceptional period and the first trimester compared with later (p < 0.001). Because of US abnormalities, pregnancy was terminated in 18 cases at the parents' request. Three infected newborns were symptomatic; all three cases were suspected at US before birth. We did not observe any symptomatic fetal infection when maternal infection occurred after 14 weeks of gestation. A number of clinically asymptomatic cases (5.5%) developed hearing loss. CONCLUSION The rate of materno fetal transmission is linearly correlated to the gestational age at infection. No severe case of congenital infection was observed if maternal infection occurred after 14 weeks of gestation.