Persistent CMV IgM Without IgG Seroconversion in an Immunomodulated Pregnant Woman: A Case Report

Congenital cytomegalovirus (CMV) infection is the most common intrauterine infection worldwide. Maternal primary infection is diagnosed with presence of IgM antibodies, detection of IgG with low avidity index, and/or IgG seroconversion in sequential serum samples. We report the first case of a pregnant woman with persistent CMV IgM positivity without IgG seroconversion, which raises significant questions regarding immune response and fetal risk assessment.

A 39-year-old woman, with a history of ankylosing spondylitis and biologic immunosuppression, exhibited persistent CMV IgM positivity and high-level viremia without IgG seroconversion over two years of fertility support follow-up. During her pregnancy, CMV IgM remained positive with transient viremia. Fetal evaluations were normal, and CMV DNA was not detected in amniotic fluid. The infant was born healthy, and, to date, no neurodevelopmental changes have been identified.

This case underscores a rare immunological profile with significant implications for CMV diagnosis and fetal risk assessment. Persistent CMV IgM without IgG seroconversion, although rare, may occur in patients undergoing immunomodulatory therapies, complicating the interpretation of maternal and fetal risk. This scenario requires individualized care and a multidisciplinary approach.