The effect of valacyclovir on secondary prevention of congenital cytomegalovirus infection, following primary maternal infection acquired periconceptionally or in the first trimester of pregnancy. An individual patient data meta-analysis.

Objective: Recent studies have shown that a dosage of 8 g/d of oral valacyclovir reduces substantially the vertical transmission rate of cytomegalovirus in women with primary cytomegalovirus infection acquired periconceptionally or during the first trimester of pregnancy. This individual patient data meta-analysis aimed to assess the effectiveness and safety of valacyclovir treatment in the secondary prevention of congenital cytomegalovirus infection.

Data Sources: MEDLINE, Scopus, Cochrane Central Register of Controlled Trials, the US registry of clinical trials (www.

Clinicaltrials: gov), and gray literature sources were searched from inception to March 2023.

Study Eligibility Criteria: Randomized controlled trials and quasi-randomized studies administering 8 g/d of oral valacyclovir in pregnant women with primary cytomegalovirus infection acquired periconceptionally or during the first trimester of pregnancy were included.

Methods: All corresponding authors of the eligible studies were contacted. Cochrane's Risk of Bias 2 and Risk Of Bias In Non-randomised Studies - of Interventions tools were used for the risk of bias assessment. The result of amniocentesis was the primary outcome of interest. A 1-stage individual patient data meta-analysis was performed, using a generalized linear mixed model, clustered by the different trials. A subgroup analysis was performed, assessing separately the effect of valacyclovir in the periconceptional period and first trimester of pregnancy.

Results: Overall, 3 studies were included in the analysis (n=527 women). Valacyclovir reduced the vertical transmission rate of cytomegalovirus (adjusted odds ratio, 0.34; 95% confidence interval, 0.18-0.61). This reduction was apparent for both periconceptional period (adjusted odds ratio, 0.34; 95% confidence interval, 0.12-0.96) and first-trimester (adjusted odds ratio, 0.35; 95% confidence interval, 0.16-0.76) infections. Moreover, valacyclovir reduced the rate of neonatal infection (adjusted odds ratio, 0.30; 95% confidence interval, 0.19-0.47), in both periconceptional period (adjusted odds ratio, 0.30; 95% confidence interval, 0.14-0.61) and first-trimester (adjusted odds ratio, 0.30; 95% confidence interval, 0.17-0.54) infections. Furthermore, valacyclovir reduced the rate of termination of pregnancy because of cytomegalovirus-associated severe fetal findings (adjusted odds ratio, 0.23; 95% confidence interval, 0.22-0.24). The gestational age at the initiation of treatment has a positive correlation with all outcomes. The overall prevalence of severe side effects was 2.1%.

Conclusion: A dosage of 8 g/d of oral valacyclovir reduced the vertical transmission rates of cytomegalovirus following primary maternal infection acquired periconceptionally or in the first trimester of pregnancy, with a low incidence of side effects.