Anticytomegalovirus IgG avidity in pregnancy: a 2-year prospective study

To analyze the practical use of the anticytomegalovirus IgG avidity and its impact on the follow-up of pregnancy. To evaluate the performance of IgG avidity to exclude the risk of congenital infection.

409 IgM-positive women without a documented seroconversion were prospectively followed. Data concerning the follow-up of the pregnancies were collected (amniotic fluid puncture and samples from the offspring). These observations were compared to those of 76 seroconversions during the same period.

High avidity excluding a primary infection within the past 3 months was observed in 270 women. As the gestational age was less than 3 months for 121 women, exclusion of a primary infection was achieved in 30% of the cases. The rate of amniotic fluid puncture was influenced by the serological result: high avidity (9%), low avidity (42%) and seroconversion (65%).

A high avidity index during the first trimester of pregnancy could reasonably be considered as a good indicator of past infection and invasive prenatal diagnosis is not necessary. Nearly 70% of the IgM-positive women could be reassured if the first serology was systematically performed before 12 weeks of gestation.