Predictive value of maternal-IgG avidity for congenital human cytomegalovirus infection

Background: Human cytomegalovirus (HCMV) is now the most common cause of vi ral intrauterine infection. Fetal damage is mostly linked to maternal prima ry infection. It is therefore important to differentiate primary from recur rent or persistent HCMV infection in pregnant females. For this purpose, Ig M tests are not reliable enough and the measurement of the IgG avidity appe ars to be presently the best method. Objective: To evaluate the performance of the measurement of HCMV-IgG avidity by a 8 M urea denaturation assay in predicting congenital infection in the offspring. Study design: Seventy-ei ght women were included in this study on the basis of a HCMV-IgM positive o r equivocal result on a first serum during pregnancy, but without a documen ted seroconversion history. The IgG avidity was measured and correlated wit h the outcome of the pregnancy. Results: In eight cases of HCMV in utero in fection the maternal HCMV-IgG avidity index was below 50%. One case of HCMV in utero infection was observed despite a high avidity index during the se cond trimester of the pregnancy. High or intermediate HCMV-IgG avidity inde xes during the first trimester of pregnancy were not associated with a cong enital infection. Conclusions: Even in the presence of an IgM positive resu lt, an HCMV-IgG avidity index above 65% on a serum obtained during the firs t trimester of pregnancy could reasonably be considered as a good indicator of past HCMV infection. In these conditions invasive prenatal diagnosis is not necessary. (C) 1999 Elsevier Science B.V. All rights reserved.