Revised Protocol for Secondary Prevention of Congenital Cytomegalovirus Infection With Valaciclovir Following Infection in Early Pregnancy

Background. A previous randomized placebo-controlled study found valaciclovir to be effective in reducing the rate of vertical cytomegalovirus transmission from mother to fetus. The better results in women infected in the first trimester compared to the periconception period were attributed to the timing of treatment. The aim of the present study was to evaluate valaciclovir efficacy in this setting using a revised protocol. Methods. All pregnant women treated with valaciclovir in 2020–2022 who met the same criteria as in the original study were identified retrospectively from the database of the same medical center. Treatment, however, was initiated earlier: up to 9 weeks or 8 weeks from the presumed time of infection in women infected in the periconception period or the first trimester, respectively. The primary endpoint was rate of vertical cytomegalovirus transmission. Results were compared with the placebo arm in the previous study. Results. Among 178 women who completed valaciclovir treatment, amniocentesis was positive for cytomegalovirus in 14 women (7.9%), significantly (P < .001) lower compared with 14 of 47 (30%) in the placebo arm in the previous study. The proportion of positive amniocentesis in the valaciclovir was significantly lower than the placebo arm both among women infected in the first trimester (14/119 vs 11/23; odds ratio [OR] = 0.15; 95% confidence interval [CI]: .05–.45, P < .001), as well as among those infected in the periconception period (0/59 vs 3/24, OR = 0; 95% CI 0–.97, P = .02). Conclusions. This study provides further evidence of the efficacy of valaciclovir in preventing vertical transmission of cytomegalovirus after primary maternal infection. Efficacy is improved with earlier treatment.