High cytomegalovirus IgG avidity among pregnant women in Northern Iran: a descriptive seroepidemiological study

Abstract Objective Human cytomegalovirus (HCMV) is a common infection worldwide and a potential risk during pregnancy due to congenital transmission. This study described the serological pattern of CMV exposure among pregnant women in northern Iran using CMV-specific IgG and IgG avidity testing. IgG avidity testing was included to differentiate recent primary infection (low avidity) from remote infection (high avidity), which is valuable in high-seroprevalence settings where IgG positivity alone offers limited epidemiological insight. Results In this retrospective cross-sectional study, 137 pregnant women aged 18–38 years attending Ayatollah Rouhani Hospital in Babol, Iran (March–December 2020) were consecutively enrolled. CMV-specific IgG and IgG avidity indices were measured using ELISA. Samples with high optical density (OD > 1.3) underwent real-time PCR. All participants were CMV IgG seropositive with high avidity indices (relative avidity index-[RAI] > 60%), consistent with prior exposure. CMV DNA was not detected in tested samples. A significant difference in mean avidity was observed between urban and rural participants ( p = 0.01), though the absolute difference was small. No significant associations were found with age, parity, education, or trimester. These findings suggest that primary maternal infection during pregnancy is likely uncommon, and congenital transmission would more probably result from non-primary infections.