Maternal Cytomegalovirus Viral Load Correlates With the Risk of Congenital Infection and With Antiviral Therapy Response in Early Pregnancy.

Background: To evaluate the impact of maternal cytomegalovirus (CMV) viral load at the time of intervention by valacyclovir (VCV) in preventing maternal-fetal transmission following primary CMV infection in early pregnancy and to assess the effect of VCV on maternal viral load kinetics. Method: We conducted a retrospective, observational, dual-center study including pregnant women referred for suspected primary CMV infection during the periconceptional period or first trimester, based on serological screening performed. Primary infection was subsequently confirmed according to predefined criteria. Maternal viral load was measured by quantitative PCR on whole blood at the time of initial evaluation in the perinatal center, before treatment initiation. Patients were analyzed according to viral load status (negative, detectable, or quantifiable) and whether they received high-dose oral VCV (8 g/day). The primary outcome was congenital CMV infection, confirmed by neonatal urine PCR. Secondary outcomes included maternal viral load kinetics and their relationship to treatment. Results: A total of 133 patients were included (90 VCV, 43 untreated). At diagnosis (median 14 weeks of gestation), 31 (24%) had negative viral load, 48 (36%) detectable, and 54 (40%) quantifiable viral load. No congenital CMV infections occurred in patients with negative viral load, regardless of treatment. Among those with quantifiable viral load, VCV was associated with lower risk of transmission compared to untreated controls (21% vs 58%; Conclusions: Maternal CMV viral load may serve as a useful prognostic indicator after primary infection in early pregnancy. Its presence could help identify a subgroup at increased risk of vertical transmission who might benefit from VCV. Conversely, negative viral load appears to be associated with a lower likelihood of fetal infection.