The successful outcome of a case of herpes simplex encephalitis (HSE) in a pregnant woman at 29 weeks gestation is reported from the Depts of Neurology and Gynecology and Obstetrics, Royal Perth Hospital and the State Health Lab Services, Perth, Western Australia. The diagnosis was suspected from the clinical presentation with fever, headache, stupor, generalized convulsion, a focal EEG, and a hypodense area in the right temporal lobe on CT. It was confirmed retrospectively from evidence of specific antibody production in the CSF. Acyclovir 800 mg/d IV every 8 hours and in a reducing regime was continued for 22 days. She recovered after 2 months and delivered a normal unaffected baby. Mother has led a normal life except for right sided focal motor and grand mal seizures controlled with anticonvulsants for 3½ years and secondary to post-encephalitic temporal lobe atrophy. The child, aged 3½ years, is well. Infection with HSV in this patient was not disseminated and did not cross the placenta. Acyclovir was non-toxic to mother and fetus when used in the 3rd trimester of pregnancy. 
COMMENT: This case of HSE is the sixth to be reported in pregnancy and the second to survive. Only one previous fetus has survived a pregnancy complicated by HSE and the mother, treated with idoxuridine, died 5 days postpartum. Acyclovir reduces mortality of neonatal HSE and is well tolerated but morbidity in surviving infants is high especially if treatment is delayed. Early diagnosis is facilitated by MRI . For a review of the natural history of HSV infection of mother and newborn and therapy of neonatal HSV infection, see Whitley RJ et al. and Infectious Disease Collaboration Antiviral Study Group. Pediatrics 1980:66:489-501.