Objective: Qinba Mountain area of Shanxi Province, China, is one of the poorest, culturally backward regions in China with a high incidence of mental retardation. To investigate whether cytomegalovirus (CMV) plays a role in the high incidence of mental retardation in this region, we studied the incidence of CMV infection during pregnancy and possible risk factors associated with CMV infection. Methods: 386 consecutive pregnant women in Qinba Mountain area were monitored for the level of a CMV-specific IgM antibody. Polymerase chain reaction was used to detect CMV in breast milk obtained within 2 weeks postpartum and urine samples of newborn infants born to actively CMV-infected mothers. Serum levels of TNF-α, IL-6, zinc, copper, iron and selenium were analyzed in CMV-infected pregnant women. Results: The incidence of CMV-active infection during pregnancy, intrauterine transmission and excretion in breast milk were 15.03, 33.33, and 39.58%, respectively. Active CMV infection during pregnancy was correlated with maternal age, education and economic status, parity, and history of obstetric complications. Those women who had active CMV infection, intrauterine transmission, or CMV excretion in milk showed higher values of TNF-α and IL-6, lower values of zinc as compared with health age-matched controls (p < 0.05). No differences were identified between studied cases and controls in the level of copper, iron, and selenium (p > 0.05). Conclusion: Theincidence of CMV-active infection during pregnancy was high in Qinba Mountain area of Shanxi Province. Zinc deficiency may be a risk factor for the development of CMV infection. TNF-α and IL-6 may be involved in the pathophysiologic process.