Congenital cytomegalovirus infection: recent advances in the diagnosis of maternal infection.

In most European countries, pregnant women are tested for cytomegalovirus (CMV) during the first trimester of pregnancy. Within the last 5 years, European laboratories have made significant progress in solving diagnostic problems linked to infection in pregnancy. With advances in CMV serology, the presence of anti-CMV immunoglobulin (Ig)M detected by a screening test such as enzyme immunoassay, can be confirmed by blot, identifying pregnant women undergoing an active or recent infection. Furthermore, primary infections that were proven if a seroconversion was observed or suspected in the presence of IgM, can now be readily diagnosed by disclosing the presence of anti-CMV low avidity in IgM-positive mothers, greatly reducing the number of women who should be considered at risk of transmitting the virus. Virologic maternal tests are not enough to diagnose a recent primary maternal CMV infection and the detection or quantification of CMV in maternal blood does not seem to be associated with a higher risk for fetal infection. A cohort of 1520 pregnant women considered at risk of transmitting the virus were followed in a longitudinal study at the University of Bologna. Women were identified as part of routine CMV screening in several Italian regions and were IgM-positive for CMV. We documented IgG seroconversion in 83 women and 1437 were IgM-positive by commercial kit.