Since primary rubella infection is usually symptomatic, there is little justification in the routine screening of the mother's blood for the presence of acute rubella infection in the first trimester of pregnancy. All suspected contacts with rubella in early pregnancy should be investigated. In many countries including the UK, the mother's blood which is taken at the antenatal booking clinic is screened for the presence of rubella antibodies and hence past immunity, and so that non-immune women may be offered rubella vaccination after birth. CMV In countries with a successful immunization policy against rubella, CMV has replaced rubella as the leading viral cause of mental handicap. Congenital infection may follow primary or recurrent CMV infection during any stage of pregnancy.
Most congenital infections are asymptomatic.
There is a 1 in 25 chance of an infant born with cytomegalic inclusion disease if the mother contracts a primary CMV infection during pregnancy. The actual figure for recurrent infection is unknown but the incidence of cytomegalic inclusion disease is much higher in infants congenitally infected following primary CMV infection than recurrent CMV infection. Unlike rubella, most CMV infections, whether primary or recurrent, are asymptomatic. Occasionally, primary CMV infection may result in an infectious mononucleosis like syndrome. Therefore, in order to monitor for active CMV infection, one would have to take repeated urine specimens throughout pregnancy for CMV culture.