Congenital cytomegalovirus (CMV) infection is the most common intrauterine infection, affecting 0.4 to 2.3 percent of live-born infants. In the United States, approximately 1 percent of newborns are infected prenatally with CMV, resulting in about 40,000 new cases annually. Although over 90 percent of infants infected with CMV are asymptomatic at birth, 5 to 17 percent develop sensorineural hearing loss, chorioretinitis, mental retardation, and neurologic deficits. Infants with symptomatic infection have more severe sequelae, with nearly 90 percent having abnormalities due to central nervous system or sensory organ damage. The study compared outcomes of CMV-infected infants born to mothers with primary CMV infection during pregnancy (primary-infection group) and those born to mothers with immunity (recurrent-infection group). Of 197 newborns with congenital CMV infection, 125 from the primary-infection group and 64 from the recurrent-infection group were followed. The primary-infection group had more severe sequelae, including higher rates of mental impairment (13 percent vs. 0 percent), sensorineural hearing loss (15 percent vs. 5 percent), and bilateral hearing loss (8 percent). The recurrent-infection group had fewer sequelae, with only 8 percent having any. Maternal antibody before conception provides protection against severe congenital CMV infection. Primary maternal infection during pregnancy is associated with more severe sequelae. The presence of maternal antibody before conception does not prevent CMV transmission but helps prevent serious injury. The study found that maternal antibody significantly reduces the severity of congenital CMV infection. The results suggest that a vaccine preventing primary CMV infection during pregnancy could prevent about 6000 damaging congenital CMV infections annually. The study highlights the importance of maternal immunity in reducing the impact of congenital CMV infection.Congenital cytomegalovirus (CMV) infection is the most common intrauterine infection, affecting 0.4 to 2.3 percent of live-born infants. In the United States, approximately 1 percent of newborns are infected prenatally with CMV, resulting in about 40,000 new cases annually. Although over 90 percent of infants infected with CMV are asymptomatic at birth, 5 to 17 percent develop sensorineural hearing loss, chorioretinitis, mental retardation, and neurologic deficits. Infants with symptomatic infection have more severe sequelae, with nearly 90 percent having abnormalities due to central nervous system or sensory organ damage. The study compared outcomes of CMV-infected infants born to mothers with primary CMV infection during pregnancy (primary-infection group) and those born to mothers with immunity (recurrent-infection group). Of 197 newborns with congenital CMV infection, 125 from the primary-infection group and 64 from the recurrent-infection group were followed. The primary-infection group had more severe sequelae, including higher rates of mental impairment (13 percent vs. 0 percent), sensorineural hearing loss (15 percent vs. 5 percent), and bilateral hearing loss (8 percent). The recurrent-infection group had fewer sequelae, with only 8 percent having any. Maternal antibody before conception provides protection against severe congenital CMV infection. Primary maternal infection during pregnancy is associated with more severe sequelae. The presence of maternal antibody before conception does not prevent CMV transmission but helps prevent serious injury. The study found that maternal antibody significantly reduces the severity of congenital CMV infection. The results suggest that a vaccine preventing primary CMV infection during pregnancy could prevent about 6000 damaging congenital CMV infections annually. The study highlights the importance of maternal immunity in reducing the impact of congenital CMV infection.