The incidence of congenital cytomegalovirus (CMV) disease is dependent on the rate of virus acquisition by susceptible women in temporal proximity to pregnancy. Information about serostatus may help to identify high-risk groups and target interventions. Each year from 1991 to 2000, cord blood specimens (surrogates for maternal serum) from 100 consecutive deliveries were obtained at three hospitals. The presence of CMV immunoglobulin G antibody was correlated with demographic data. Overall, 58% of 2992 women were seropositive. After stratification by socioeconomic status (SES), nonwhite race was strongly associated with seropositivity (odds ratio, 3.0; 95% confidence interval [CI], 2.5 to 3.8), and after stratification by race, lower SES also was associated (odds ratio, 2.0; 95% CI, 1.7 to 2.3). There were no trends in seroprevalence over time in any demographic group. However, among white women 21 to 29 years of age, a significant association was found with later birth cohort. Seropositivity ranged from 40% among older, white primigravidas of upper SES to 89% among older, nonwhite, multigravid women of lower SES. These data suggest high rates of CMV transmission among nonwhite women of lower SES. Because these women tended to deliver infants at younger ages, delaying pregnancy even a few years might reduce the incidence of congenital disease. In contrast, most white, upper SES women remain susceptible to primary infection during their childbearing years. Such women born after 1975 may be more likely to reach the childbearing years with CMV immunity as compared with women born before then.