Objective: This study estimated CMV molecular prevalence in placental biopsies as well as in umbilical blood cord and its correlation with infection of pregnant women and their newborns to determinate vertical transmission risks. Design: A cross-sectional study Setting: Obstetric Center of the University Hospital in Rio Grande, Brazil Population: 496 pregnant women and their newborns Methods: Biopsies were collected from peripheral and central portions of each placenta, separated on fetal and maternal interfaces, matched with cord blood, totaling 1488 samples. PCR technique and sequencing were used to investigate the prevalence. Main Outcome Measures: Bivariate and multivariate analysis were performed to determinate sociodemographic, clinical and gynecological data associated to CMV vertical transmission. Results: CMV DNA was found in 5.2% of placental maternal interface and 5.4% of fetal interface with a positive result for CMV in 3.6% in cord blood. In more than 90% of the cases, there was no match between positive CMV DNA cord blood and positive placentas, indicating vertical transmission ascending from genital tract. The income factor (less than 1 minimum wage) was significantly associated with prevalence of CMV in placentas (p = 0.03). In cord blood samples, non-white skin color and early age at the onset of sexual intercourse were risk factors associated with the infection (p = 0.04). Conclusions: The occurrence of CMV DNA found in cord blood suggests the pattern observed appears to be ascending from genital tract of asymptomatic mothers. Economical and environmental factors present a negative impact on fetal-maternal transmission of cytomegalovirus.