OBJECTIVE: To determine threshold cytomegalovirus (CMV) infectious rates and treatment effectiveness to make universal prenatal CMV screening cost-effective. STUDY DESIGN: Decision analysis comparing cost-effectiveness of two strategies for the prevention and treatment of congenital CMV: universal prenatal serum screening and routine, risk-based screening. The base case assumptions were a probability of primary CMV of 1% in seronegative women, hyperimmune globulin (HIG) effectiveness of 0%, and behavioral intervention effectiveness of 85%. Screen-positive women received monthly HIG and screen-negative women received behavioral counseling to decrease CMV seroconversion. The primary outcome was the cost per maternal quality-adjusted life year (QALY) gained with a willingness to pay of $100,000 per QALY. RESULTS: In the base case, universal screening is cost-effective, costing $84,773 per maternal QALY gained. In sensitivity analyses, universal screening is cost-effective only at a primary CMV incidence of more than 0.89% and behavioral intervention effectiveness of more than 75%. If HIG is 30% effective, primary CMV incidence can be 0.82% for universal screening to be cost-effective. CONCLUSION: The cost-effectiveness of universal maternal screening for CMV is highly dependent on the incidence of primary CMV in pregnancy. If efficacious, HIG and behavioral counseling allow universal screening to be cost-effective at lower primary CMV rates.