Toxoplasma gondii is one of the world's most common parasites. Primary infection of the mother during pregnancy can lead to transmission to the fetus with risks of brain and eye lesions, which may cause lifelong disabilities. France instituted a national program based on monthly retesting of susceptible pregnant women to reduce the number of severe cases through prompt antenatal and postnatal treatment and follow-up. To evaluate the ability of the French prenatal retesting program to reduce the lifetime costs of congenital toxoplasmosis. We measured and then compared the costs and benefits of screening vs. not screening using decision-tree modelling. It included direct and indirect costs to society of treatment and care, and the lifetime lost earnings of children and caregivers. A probabilistic sensitivity analysis was carried out. Total lifetime costs per live born child identified as congenitally infected were estimated to be euro444 for those identified through prenatal screening vs euro656 for those who were not screened. Estimates were robust to changes in all costs of diagnosis, treatment, and sequelae.