Maternal immunity and prevention of congenital cytomegalovirus infection.

CONTEXT Vaccine development to prevent congenital cytomegalovirus (CMV) infection has been impeded by the uncertainty over whether maternal immunity protects the fetus. OBJECTIVE To determine whether the presence of maternal antibodies to CMV significantly reduces the risk of congenital CMV infection in future pregnancies. DESIGN, SETTING, AND PARTICIPANTS Cohort study of 3461 multiparous women from a population with a high rate of congenital CMV infection who delivered newborns screened for congenital CMV infection between 1993 and 1998, and whose cord serum specimen from a previous delivery could be retrieved and tested for antibody to CMV. MAIN OUTCOME MEASURE Congenital CMV infection according to maternal immune status, age, race, parity, and socioeconomic status. RESULTS Of 604 newborns born to initially seronegative mothers, congenital CMV infection occurred in 18 (3.0%). In contrast, of 2857 newborns born to immune mothers, congenital CMV infection occurred in 29 (1.0%) Two factors, preconception maternal immunity (adjusted risk ratio, 0.31; 95% confidence interval, 0.17-0.58) and maternal age of 25 years or older (adjusted risk ratio, 0.19; 95% confidence interval, 0.07-0.49), were highly protective against congenital CMV infection. No other factors were associated with a reduction in the risk of congenital CMV infection. CONCLUSION Naturally acquired immunity results in a 69% reduction in the risk of congenital CMV infection in future pregnancies.