A review of the literature shows that 36% of pregnant women are not immunized against cytomegalovirus; 2.11% of these patients will have a primary infection during their pregnancy. The fetal transmission rate is 30%. Viruria after delivery is the unique proven sign of infection; but is only present in 4 to 5 infants per 1,000 births. Of those, 17% will be symptomatic at delivery and 10% will develop sequels as late as seven years later. CMV can be reactivated during pregnancy. These cases are less dangerous but the fetal risk is always present.
Gaudy, V., Lamy, M. E., Mulongo, N. K., & Van Lierde, M. (1992). Cytomégalovirus et grossesse : Risque fœtal et néonatal. Journal de gynécologie, obstétrique et biologie de la reproduction, 21(7), 779-790. https://hdl.handle.net/2078.5/131985 (Original work published 1992)