Is neonatal viremia a possible predictor of the timing of maternal infection in asymptomatic congenital cytomegalovirus infection? A retrospective study

Background: Asymptomatic congenital cytomegalovirus (acCMV) infections represent 85–90% of all congenital CMV infection. The incidence of late-onset sequelae in these cases significantly contribute to the burden of CMV disease. The timing of maternal infection (TMI) has been identified as the main predictor of late-onset sequelae in acCMV infants, and follow-up programs in Europe are currently calibrated according to the TMI. Our aim was to evaluate neonatal viremia as a possible predictor of the TMI in acCMV infections. Methods: Plasma viral loads (PVLs) were assessed in the first month of life in a population of acCMV-infected newborns delivered by women who suffer a primary CMV infection during pregnancy. TMI was assigned to a trimester of pregnancy according to the maternal serological screening. PVLs were evaluated in relation to the TMI and gestational age (GA) at birth. Results: One hundred and ten newborns were, respectively, assigned to preconceptional (6.4%), 1st (27.3%), 2nd (38.2%), and 3rd (28.2%) trimester infections. Median neonatal PVLs values were significantly different between groups (p < 0.001). First-trimester infections exhibited significantly higher PVLs when compared with third-trimester ones (p < 0.001). Overall, PVLs showed an inverse correlation with GA at birth (p = 0.003). Conclusions: Median neonatal PVLs are significantly higher in 1st trimester infections if compared with 3rd trimester ones, but a wide overlap between PVL values prevent their possible use as a predictor of the TMI. In our population, a significant inverse relationship, mainly dependent on 1st and 2nd trimester infections, is demonstrated between PVLs and GA. Overall, fetal viremia is already decreasing weeks before the term of pregnancy.