Gestational age-dependent dynamics of transplacental CMV and VZV IgG transfer: Weekly comparative analysis in preterm and full-term neonates (24-41 weeks).

Background: Transplacental transfer of maternal IgG antibodies promotes foetal immunity against cytomegalovirus (CMV) and varicella-zoster virus (VZV) infections. Comprehensive data on antibody transfer across gestational ages, particularly before 28 weeks, remain limited.

Methods: This prospective cohort study analysed paired maternal and newborn blood samples from n = 564 mother-child pairs (gestational weeks 24-41). Anti-CMV and anti-VZV IgG concentrations were measured using ELISA-tests and CMV neutralising capacity was assessed using an in-house cell culture-based assay.

Results: Newborn antibody concentrations were significantly lower than maternal levels at 24-29 weeks for both CMV and VZV (p < 0.05). Equilibrium was reached at weeks 30-34 for CMV and 30-33 for VZV. Beyond week 35 for CMV and week 34 for VZV, newborn concentrations significantly surpassed maternal levels (p < 0.05). CMV neutralisation capacity in neonates was significantly lower during weeks 24-29 compared to weeks 30-34 (p < 0.05) and weeks 35-41 (p < 0.01), showing progressive improvement during gestation. Maternal neutralising capacity remained constant across all gestational intervals. The newborn-maternal difference in neutralising capacity was progressive: minimal at weeks 24-29, significantly greater at weeks 30-34 (p < 0.05), and maximum levels in neonates at weeks 35-41 (p < 0.01), indicating enhanced qualitative antibody transfer. Neither gender nor twin-pregnancies showed a significant effect on antibody transfer.

Conclusions: Gestational age-dependent transplacental CMV and VZV IgG antibody transfer occurs as early as week 24. Extremely preterm infants showed significantly lower antibody concentrations and CMV neutralising capacity. Targeted prevention strategies for this vulnerable population and further studies investigating the preferential materno-foetal transfer of antibodies with high neutralisation capacities are warranted.