LB20. Valacyclovir to Prevent Vertical Transmission of Cytomegalovirus After Maternal Primary Infection During Pregnancy

BACKGROUND: Cytomegalovirus (CMV) is the most common cause of congenital infection in humans. The highest risk of fetal injury follows a maternal primary infection early in pregnancy. Despite the potential for severe fetal injury, to date there are no proven means to prevent viral transmission. Valacyclovir is an antiviral drug proven effective in decreasing the risk for CMV infection among transplant recipients. Valacyclovir is safe for use in pregnancy, and concentrates in the amniotic fluid without accumulating. A dose of 8 g/day creates therapeutic drug levels in the amniotic fluid and fetal blood. METHODS: This is a randomized, double-blind, placebo-controlled study comprising pregnant women with serologic evidence of primary CMV infection during the periconceptional period and first trimester. After informed consent, patients were randomly assigned to a treatment group (8 g/day of Valacyclovir) or control group (placebo). Treatment was initiated at the time of serological detection, and continued until amniocentesis. The primary endpoint was the rate of vertical transmission of CMV—determined by amniotic fluid CMV PCR. Secondary endpoints included evidence of symptomatic congenital CMV infection—in utero or postnatally. RESULTS: One hundred women were recruited, 90 were included in the data analysis; 45 patients received Valacyclovir and 45 placebo. There were 2 twin pregnancies, and therefore 92 amniocentesis Amongst the Valacyclovir group, 5 (11.1%) amniocentesis were positive for CMV, compared with 14 (29.8%) in the placebo group (P GLMM = 0.03), corresponding with an odds ratio of 0.29 (95% CI: 0.09–0.90) for vertical CMV transmission. Amongst patients infected during the first trimester, a positive amniocentesis for CMV was significantly (P = 0.02) less likely in the Valacyclovir arm (2/19) compared with placebo (11/23). No significant differences (P = 0.91) in CMV-positive amniocentesis were observed between study arms amongst patients infected periconceptionally. CONCLUSION: Valacyclovir at a dose of 8 g/day is effective in reducing the rate of fetal CMV infection following early maternal primary infection during pregnancy. The drug reduces the rate of fetal infection by 71%. DISCLOSURES: All authors: No reported disclosures.