Herpes encephalitis during pregnancy: failure of acyclovir and adenine arabinoside to prevent neonatal herpes.

A gravid woman with herpes Type II encephalitis delivered an infant with herpes neonatorum despite therapy with acyclovir. Acyclovir was not measurable in the baby's serum 10 h after birth. The viral isolate was sensitive to acyclovir in vitro, and the neonatal infection responded to treatment with the drug. Prenatal antiviral therapy may be ineffective in preventing intrauterine herpesvirus infection.