 The infection with cytomegalovirus CMV is the first cause of congenital neurological handicap of infectious origin. It is probable that the neonatal viral load is correlated with becoming of infected new-born babies. Among the active antiviral treatments against CMV, valacyclovir is the only whose fetal and maternal tolerance was evaluated during the pregnancy. Its harmlessness and its aptitude to decrease the CMV viral load justify to evaluate it in a study against placebo. Decrease the fetal viral load could make possible to decrease symptomatology neonatal in a group of infected fetuses. 