Prenatal indicators of congenital cytomegalovirus infection.

Objective: To assess the validity of a diagnostic protocol designed to predict the outcome of newborns of mothers suspected to have primary cytomegalovirus (CMV) infection during the first 4 months of pregnancy.

Study Design: Anti-CMV immunoglobulin (Ig) M detection by enzyme immunoassay and immunoblot together with the determination of anti-CMV IgG avidity allowed us to classify 456 women as (1) uninfected, (2) undergoing either a primary or a recurrent infection, or (3) having an undefined serologic condition. Prenatal diagnosis was carried out at 21 to 23 weeks' gestation for women. The presence of the virus in the amniotic fluid was determined by culture, polymerase chain reaction, and quantitative polymerase chain reaction. Macroscopic and histologic examinations were undertaken on tissue from aborted fetuses, whereas for newborns culture was performed on urine sampled during the first week of life.

Results: Congenital infections were found exclusively among women undergoing a primary infection. The quantitative determination of CMV DNA in the amniotic fluid of at least 10(3) genome equivalents gave a 100% certainty of detecting an infected fetus. Higher viral loads were associated with fetuses or newborns with symptoms.

Conclusions: IgM tests and the IgG avidity determination can identify all women at risk of transmitting CMV. Furthermore, a high CMV DNA load in amniotic fluid could be an indicator of symptomatic congenital infection at a relatively early stage of pregnancy.