Controversies in the natural history of congenital human cytomegalovirus infection: the paradox of infection and disease in offspring of women with immunity prior to pregnancy.

Human cytomegalovirus (HCMV) is the most common virus infection in the developing fetus. A fraction of infants infected in utero develop significant life-threatening and organ-threatening disease with over 90% of infected infants exhibiting no clinical evidence of infection in the newborn period. However, about 10% of all infected infants will develop long-term sequelae. Early studies stressed the importance of primary maternal HCMV infection during pregnancy as a critical determinant of intrauterine transmission and outcome. This concept serves as the foundation for the development of prophylactic vaccines and biologics such as HCMV immune globulins. More recently, studies in maternal populations with high HCMV seroprevalence have challenged the concept of protective maternal immunity. Findings from multiple studies suggest that preexisting maternal HCMV immunity provides at best, partial protection from disease in the infected offspring and similarly may have limited impact on intrauterine transmission. This brief review will provide some considerations about the apparent paradox of maternal HCMV immunity and congenital infection.